The Iran-backed Houthi rebels and Saudi Arabia ratcheted up Mideast violence Sunday with attacks on each other’s airports, the day after the terrorists’ strike on Riyadh that killed 13, including an American.

The Houthis fired more missiles at the King Khalid International Airport in Riyadh, causing a fire at one of the air hub’s passenger terminals, according to the governing Saudi-led coalition in Yemen, where the opposing Houthis are based.

Coalition spokesman Major General Turki al-Malki said at least one projectile hit the airport’s Terminal 4, with another cruise missile intercepted near the facility.

The Houthis, who took credit for Saturday’s deadly airstrike on the airport, said the assault was part of a three-phased operation against transit hub, with the group claiming that four bombardments have been carried out so far in the past 24 hours. The rebels also attacked the airport Thursday, killing three.

“We reiterate our warning to all international companies, experts, employees, workers, and travelers from all over the world to not operate flights to Saudi airports, as they are unsafe, except for the airports and airspace of the holy cities of Mecca and Medina,” the terror group said in a statement.

Saudi’s civil-aviation authority confirmed that civilians were injured in the latest attack, but officials did not specify the casualties or extent of physical damage incurred by the strike.

An Indian national who was wounded in Saturday’s strike at the airport died from their injuries Sunday, bringing the death toll up to 13, according to the Indian embassy in Riyadh.

The attacks on the airport were in response to Saudi Arabia’s airstrikes on Houthi territory in Yemen, including its airport in the capital of Sanaa, Houthi spokesman Yahya Saree claimed.

Saudi Arabia also launched a new attack on the Sanaa International Airport on Sunday, with the Saudi-backed forces reportedly firing 124 airstrikes over the weekend, Houthi officials said.

There were no initial reports of casualties or damages at the Sanaa airport, according to the state-controlled Saba News Agency.

The attack came after the Saudi-backed coalition in Yemen issued a statement vowing a strong response to the Houthi “terrorist” attack in Riyadh that killed 13 and left more than 300 others wounded.

The weekend strikes served as a major escalation in the renewed civil war between the Houthis and the internationally recognized government in Yemen.

President Trump has suggested that the US, which is at war with Iran, may join Saudi Arabia in launching retaliatory attacks against the Houthis.

Saudi Crown Prince Mohammed bin Salman has reportedly been pushing Trump to take military action against the Houthis, who agreed to a cease-fire with the US last year.