KANDAHAR, Afghanistan -- Taliban fighters killed up to 16 men after learning they had registered for Afghanistan's U.S.-backed national elections, the deadliest attack yet in a campaign aimed at sabotaging the nation's first free vote, officials said Sunday.
The assault raised security fears and added to doubts over whether Afghanistan is ready to hold elections as planned in September -- and increased pressure on NATO leaders meeting Monday in Turkey to deploy more peacekeepers here.
The killings took place Friday on a road in southern Uruzgan province and various reports put the number of dead at 10 or 16. News of the deaths emerged a day after a bomb ripped through a bus carrying female election workers in the eastern city of Jalalabad, killing two of them and wounding 13. A spokesman for the Taliban claimed responsibility.
Time is running out for the joint U.N.-Afghan electoral authority to decide on the polling date if the election is to be held according to schedule.
According to the electoral law, the date must be announced 90 days beforehand -- meaning by July 2, if polling takes place on the last day of September.
The Uruzgan attack, which left between 10 and 16 people dead, underscored the risks faced by Afghans if they want to exercise their democratic rights, particularly in lawless areas of the country, plagued by Taliban-led insurgents who have threatened more attacks against election workers and voters.
Rozi Khan, the Uruzgan police chief, said assailants stopped a van carrying 12 men on a road about 18 miles from the provincial capital, Tirin Kot.
When the gunmen searched their documents and found that they had registered to vote, they opened fire. Two men escaped and alerted police, who found the 10 bodies but have made no arrests.
Obaidullah Khan, the top political administrator of the victims' home district of Uruzgan, confirmed the attack but said 16 people had died, and only one man had survived.
It was impossible to immediately account for the discrepancy.
Obaidullah Khan said six or seven attackers had launched the assault, while others hid in rocks nearby.
Afghan President Hamid Karzai and the U.S. military is adamant the election can stick to schedule -- although with only three days left for voter registration, only about half of eligible people have signed up nationwide.
U.N. spokesman Manoel de Almeida e Silva said Sunday he expected the electoral authority to extend in some areas of the country the end-of-June deadline for registration, to address regional and gender imbalances in the electoral rolls.
Just over 5 million voters have signed up so far, and only about one-third of them are women. Remote, Pashtun-dominated areas where insurgents are most active are lagging behind other regions.
"The southeast is an area of concern, the south as well," de Almeida e Silva told a news conference in Kabul.
Jean Arnault, the top U.N. envoy in Afghanistan, has urged NATO leaders who will meet at the Istanbul summit to send more troops ahead of the vote. The alliance has 6,400 peacekeepers here, largely confined to Kabul.
But Arnault insisted Sunday that attacks like the bombing against the female election workers in Jalalabad should not be allowed to scuttle the election process.
"The best way we can pay tribute to the two women killed is to rededicate ourselves to this process," he said during a visit to some of the bomb victims and their families.
On Sunday, authorities in Jalalabad questioned the driver of the bus targeted in the bombing. The driver allegedly fled shortly before the blast.
"He is from Jalalabad, but we're not 100 percent sure he did this," said provincial governor's spokesman Faizan, who uses only one name. He declined to identify the suspect further.
Seven badly injured passengers -- including one child -- have been transferred to Kabul and the main U.S. military base at Bagram, north of the capital, for treatment, de Almeida e Silva said.
He said that voter registration was continuing in surrounding Nangarhar province despite the attack, although the movement of female election staff had been suspended in the south, southeast and east of the country.
Because of religious and cultural sensitivities in this deeply Islamic country, voter registration is segregated between the sexes.
Associated Press Writer Matthew Pennington in Kabul contributed to this report.