ByZoya Mateen and Vikas Pandey

BBC News, Delhi

The founder of India's "cockroach" protest movement, Abhijeet Dipke, has been detained by police in Delhi ahead of a planned march in the heart of the capital.

His detention follows a police warning against holding Friday's march, with thousands of security personnel deployed across the city to prevent the gathering.

Dipke's youth-led Cockroach Janta Party (CJP), which has drawn thousands onto the streets in recent months, is demanding the resignation of India's election chief over alleged irregularities in voter lists. The Election Commission denies this.

The group had asked supporters to come to a park in Connaught Place, one of Delhi's busiest commercial districts, to wave the Indian flag.

It is the second time in less than a week that Dipke has been detained ahead of a protest. Last Saturday, police boarded his plane shortly after it landed in Delhi and took him away before he could reach a planned demonstration.

Police barricades and mass detentions prevented thousands of other protesters from reaching the venue. Dipke was released the following day, but two other CJP leaders were later jailed for five days after entering Jantar Mantar, a protest site recently declared off-limits by police.

On Friday, the police served a notice to Dipke, alleging he had asked his supporters to gather without permission and warned him of criminal action if his group defied restrictions on public gatherings.

Shortly after, the CJP issued fresh instructions, asking supporters to arrive in the park at Connaught Place in groups of fewer than five, unfurl the Indian flag, take a photograph and leave.

"Waving the Tiranga (tricolour flag) is not a crime," the group said in a social media poster, urging protesters to share their photographs online.

These instructions marked a shift from the large gathering originally planned at Central Park, as the movement sought to press ahead despite police restrictions.

Barely five months old, the CJP began as an online campaign in May after India's chief justice likened some unemployed young people to cockroaches. Dipke embraced the insult and turned it into a rallying cry.

By July, the group had become a formidable force, drawing thousands of young people into protests over leaked examination papers. A march towards Parliament in July descended into clashes with police, bringing the movement wider attention and intensifying pressure on the government. The unrest eventually forced the resignation of India's education minister, Dharmendra Pradhan.

Police have pointed to those earlier protests to justify stopping Friday's march. In the notice served to Dipke, they accuse the CJP of defying restrictions on previous demonstrations and say attempts to march towards parliament led to violence and damage to property.

They warn that another large gathering, this time in the busy commercial district of Connaught Place, could disrupt traffic, force businesses to close and block access for emergency vehicles.

Authorities have also closed Central Park, where the protesters planned to gather, for two days, citing "administrative reasons". Police said a small group could instead wave the national flag and sing the anthem at another location it gave.

Dipke, however, refused to back down, insisting that the march, named Lehra Do Tiranga, or Wave the Tricolour, would go ahead even if it means his arrest.

In a video message, he had urged those unable to travel to Delhi to join the protest from wherever they were, raising the Indian flag in their own towns and cities.

In Connaught Place, small groups of protesters waved Indian flags and shouted slogans, but there was little sign of the large turnout the movement had drawn in previous demonstrations.

The police presence, meanwhile, had grown considerably. More officers emerged from buses stationed around the area, while a large crowd of journalists gathered to cover the happenings of the evening.

For now, the security operation and media presence appeared to far outnumber the protesters themselves.

At issue is a sweeping revision of electoral rolls, known as Special Intensive Revision (SIR), that critics say has removed more than 130 million names, putting legitimate voters at risk of losing their right to vote.

The CJP wants Chief Election Commissioner Gyanesh Kumar to resign, accusing the poll panel of favouring Modi's ruling Bharatiya Janata Party (BJP). Both the commission and the government deny the allegations.

Friday's march comes less than a week after police prevented the movement's last mass demonstration from taking place, detaining its leaders and deploying officers across the capital before protesters could assemble.

Dipke and two senior organisers, Saurav Das and Ashutosh Ranka, were detained from within the aircraft upon landing in Delhi.

The capital was put under a sweeping security lockdown. Tens of thousands of police and paramilitary personnel had fanned out across Delhi, sealing roads, shutting metro stations and intercepting protesters long before they could reach Jantar Mantar, where the CJP had planned its mass demonstration.

The BBC witnessed dozens of people being detained, including journalists and students. In footage from across Delhi, protesters could be seen shouting as police seized them by the arms, dragged them across the pavement and pushed them into waiting buses.

Those who managed to gather elsewhere were swiftly dispersed. There were also reports of protesters being assaulted by police.

The BBC captured footage, external of a policeman slapping a detained protester inside a bus. The Delhi police did not respond to questions about the use of violence against protesters.

The scale of the crackdown drew widespread outrage, with the CJP likening the police action to India's Emergency, when civil liberties were suspended between 1975 and 1977.

Delhi police defended the measures as necessary to maintain public order and prevent unauthorised gatherings.

Dipke, Das and Ranka were released on Sunday after agreeing to maintain peace and good behaviour.

Police then took Jantar Mantar off Delhi's list of approved protest sites, telling demonstrators to go instead to Ramlila Maidan, Burari Ground or CBD Ground.

But Jantar Mantar is no ordinary patch of ground. Built in the 18th Century to study the stars, the observatory sits near parliament and has long been one of India's most recognisable stages for public dissent.

The CJP accused the authorities of pushing protesters away from the seat of power to make their demonstrations less visible and easier to ignore.

On Tuesday, Das and Ranka returned anyway, bringing a handful of supporters. They unfurled the Indian flag and shouted slogans against Kumar. Police said they had entered the restricted site without permission, some by climbing over a locked gate, and violated the conditions of their earlier release.

The following day, Das and Ranka were sent to jail for five days in judicial custody. Another organiser, Ajinkya Shinde, was released on a bond to maintain peace and good behaviour.

With two of its key organisers behind bars, the CJP heads into Friday's protest with its leadership depleted, though Dipke insists the march will go ahead and he does not intend to back down.

"I also may be jailed after this, but I am not worried. Tricolour is my pride and I will raise it," he said in a video message.

The CJP's campaign is unfolding alongside a separate wave of protests by India's opposition parties, which have also accused the Election Commission of manipulating voter rolls to benefit the BJP.

Last week, opposition leader Rahul Gandhi and other lawmakers attempted to march to the commission's headquarters in Delhi but were stopped by police and detained. Opposition politicians have since taken their grievances to President Droupadi Murmu and marched towards the Supreme Court.

Among those at Monday's march was Neha Bora, a feisty leader of the left-wing All India Students' Association (AISA), who has emerged as another prominent face of the demonstrations.

Detained while leading protesters last Saturday, she was later seen marching with Gandhi and his sister Priyanka Gandhi Vadra.

Although the CJP, student organisations and opposition parties have largely protested separately, their demands have increasingly converged. Gandhi has condemned the arrests of CJP organisers and called for Jantar Mantar to be reopened to peaceful demonstrators.

Home minister Amit Shah, meanwhile, has accused opposition parties of spreading falsehoods about the voter-verification exercise and defended the Election Commission's independence.