KABUL, Afghanistan (AP) — Police set up extra checkpoints across Afghanistan on Friday to scan for suicide bombers and insurgents a day ahead of parliamentary polling that will test the government's ability to hold a legitimate election after last year's disastrous presidential vote.

Whether the vote is safe and fair will reverberate strongly with the international coalition supporting Afghanistan with 140,000 troops and billions of dollars, following a fraud-marred presidential vote in August 2009 that nearly undermined President Hamid Karzai's credibility with his international backers.

About 2,500 candidates are vying for 249 parliamentary seats, which are allocated among the 34 provinces according to population.

Results of the races for the relatively weak legislature are unlikely to affect Karzai's administration. However, the elections will be an indicator of the strength of the insurgency as NATO and Afghan forces work to secure polling stations in volatile areas amid Taliban threats.

The Taliban have warned of countrywide attacks on Saturday targeting voters and election workers.

In eastern Khost province, police said mosques were blanketed with leaflets overnight promising a violent vote.

"The people of Khost should not go to the voting centers. If anyone goes, we will punish them," the notes said, according to provincial police chief Abdul Hakim Isaqzai.

NATO said Friday that coalition forces detained two insurgents in Khost province, including one who was "actively" planning attacks during the elections.

Afghan security forces patrolled the mountains and hills that circle Kabul to prevent insurgents from setting up rocket-firing points, Deputy Police Chief Khalilullah Dastyar said. Police used bomb-sniffing dogs while searching every car heading along main roads into the city.

"Also at all the voting centers, police are already deployed," Dastyar said.

The streets were relatively empty as is typical for a Friday — which is not a working day in Afghanistan.

In volatile Kunar province in the northeast, police said they have not been able to deploy soldiers to remote areas but have set up checkpoints at the roads into the provincial capital. They are stopping vehicles and questioning anyone wearing a burqa — the full-body robe often worn by Afghan women in conservative areas. Insurgents previously have hidden under burqas to get past checkpoints.

"We are talking to anyone with a burqa to make sure it's actually a woman," said Khalilullah Zaiyi, the provincial police chief.

With a raging insurgency, hardly anyone is predicting a free and fair vote by Western standards.

"This is probably one of the worst places and the worst times to have an election anywhere in the world. We have to put it into perspective," said Staffan de Mistura, the top U.N. envoy to Afghanistan.

"We don't expect a fair and transparent election. What we expect is an acceptable election," said Haroun Mir, director of the Afghanistan Center for Research and Policy Studies, a Kabul-based think tank.

The hope is that Afghans and the international community will be able to proclaim it an improvement over the August 2009 presidential vote, when an U.N.-backed anti-fraud watchdog found rampant fraud in Karzai's re-election.

Violence already has been a problem in the run-up to Saturday's vote. At least 21 people have been killed in election-related violence, including four candidates, according to observer groups.

On Thursday, 18 election workers were kidnapped from a house in Badghis province, said provincial government spokesman Sharafuddin Majidi. He said local residents told the government that the workers had been taken by the Taliban. Further details were not available.

In eastern Ghazni province, a Taliban operative told The Associated Press that the group had warned residents they would be targeted if they left their homes or opened shops anytime Saturday or Sunday.