At least 11 people, including election workers, have been killed in Afghanistan’s north when a roadside bomb blew up their bus, according to a local official.

The governor of the northern province of Samangan told the Reuters news agency that the blast came on Saturday evening, after polls closed in a second-round, run-off vote to elect a successor to President Hamid Karzai.

Four of the victims were employees of the country's election commission, which organised the vote, the governor’s spokesperson told the AP news agency.

In a separate incident, the Taliban cut off the fingers of 11 civilians on Saturday in western Herat province to punish them for voting in the presidential runoff, police spokesman Raoud Ahamdi told AP.

The Taliban had warned people not to participate in the vote, which is set to mark the country's first democratic transfer of power.

The AFP reported that there were at least 150 minor attacks on the polling day, including a Taliban rocket that hit a house near a polling station, killing five members of the same family.

Despite the unrest, millions of Afghans cast their ballots. The UN praised the elections and congratulated the "courageous" Afghans who participated in it.

Fraud alleged

The polls result, due out next month, will confirm whether former foreign minister Abdullah Abdullah or ex-World Bank economist Ashraf Ghani will lead Afghanistan into a new era of declining international military and civilian assistance.

The two candidates came top of an eight-man field in the April first-round election, triggering the run-off as neither reached the 50 percent threshold needed for outright victory.

Abdullah secured 45 percent of the vote with Ghani on 31.6 percent. Counting the ballot will take weeks. The preliminary result is due on July 2 and a final result on July 22.

While high turnout may lend legitimacy to the winner if the gap between the two candidates is clear, a close count could mean a contested outcome.

Both candidates swiftly alleged fraud after the closure of the polls on Saturday.

"We know there has been fraud, you have seen it, we have seen it," Abdullah said.

Ghani called for a full investigation into vote-rigging, saying "unfortunately there were cases of security forces involved in fraud, we have the evidence".

A smooth handover in Afghanistan's first democratic transfer of power would be a major achievement for the 13-year US-led effort to establish a functioning state after the depredations of the Taliban era.

President Karzai, who has ruled Afghanistan since 2001 and was re-elected in a 2009 vote marred by ballot-box stuffing, is constitutionally barred from a third term in office.

Source: Agencies