Sweden's left- and right wing political blocs are in a tight race in Sunday's general election, with current conservative Prime Minister Ulf Kristersson promising cabinet jobs for hard-right allies if he remains at the helm.

Latest polls show a narrow lead for the left grouping, which is backing the Social Democrats' Magdalena Andersson to return to power.

Kristersson has been supported in government by the hard-right Sweden Democrats (SD), who have neo-Nazi roots.

National security, gang crime and welfare spending are among the key issues, but the potential for the anti-immigration SD to enter government could also influence the outcome.

In Sweden, there are two major political blocs - with four parties on the right and four on the left, so Swedes are used to coalition and minority governments.

More than eight million people are eligible to vote in the election for Sweden's Riksdag.

A poll on Friday, commissioned by Swedish news service Ekot, shows the left-wing bloc with 50.8% of the vote, compared with the right-wing bloc on 47.6% - a lead of 3.2%.

The centre-left Social Democrats, who have pledged higher public spending, lead the polls, with 28.6%, while on the right the Sweden Democrats are behind them with 18.3%, according to the Ekot survey.

Other opinion polls on Friday also put the left-wing bloc in the lead.

The Social Democrats have regularly led Swedish governments since World War Two and have been the country's dominant political force for much of the last century.

In stark comparison the SD, founded by Nazi sympathisers in the 1980s, were for decades shunned by the mainstream.