A bomb blast killed at least five people and wounded 34 in the western Afghan city of Herat on Sunday, raising fresh concern about security for landmark elections.

The United Nations said the blast was the latest in a string of violent incidents that underscored the need for the immediate deployment of more international troops to protect the Oct. 9 presidential vote and parliamentary elections in April.

The explosion came less than two days after the announcement of the poll dates and just ahead of a ceremony to mark the start of disarmament of Herat's militia forces, part of a drive seen as crucial to creating conditions for a free and fair vote.

The bomb exploded outside a military post near a busy morning market in the ancient city, which is not far from the Iranian border, provincial spokesman Ghulam Mohammad Masoan said.

"The death toll has reached five, a child is among them. And we have 34 wounded," said Nasir Habib, a doctor at the main Herat hospital, adding that the toll could rise as some were critically hurt. All victims were civilians and included women and children.

Herat police chief Zia Uddin Mahmodi said the bomb might have been hidden in a bucket and the Taliban could be to blame.

Lieutenant-Colonel James Hand, head of a U.S. civilian-military team helping with security in Herat, said there were also reports it was a bicycle or a motorcycle bomb. He said he had no clue as to who might have carried out the attack.

The Taliban, ousted by U.S.-led forces in late 2001, have vowed to disrupt the elections. Militant attacks have killed hundreds this year, including election workers, but most of their activity has been in the volatile south and east.

Masoan called the bomb the work of "those people who do not want a stable Herat" -- an apparent reference to rivals of the powerful provincial governor, Ismail Khan.

Herat has long been seen as one of the more stable parts of the country, but in March fighting erupted between forces loyal to a government military commander and Khan's militia, in which Khan's son, Aviation Minster Mirwais Sadiq, was killed.

President Hamid Karzai sent national troops to intervene but commanders loyal to Khan, who forced those of the rival commander out of the city, said they were not needed.

Disarming fighters

The ceremony marking the start of disarmament of Khan's militia began three hours after the blast, at a military base 10 km (six miles) away.

Disarming of irregulars commanded by strongmen like Khan has moved much more slowly than hoped, with only about 10,000 demobilized out of a total of some 50,000.

Some commanders, including Khan, have warned that disarming their forces will increase instability, especially while a new national army -- currently 12,000 strong -- is still so small.

Analysts say some commanders will also have been angered by the decision to hold the parliamentary polls six months later than the presidential vote, seeing an early election as their best chance to consolidate their positions.

At a news briefing, U.N. Special Representative Jean Arnault did not rule out the possibility that blasts like the one in Herat might be the work of those opposed to disarmament.

"There is very much a possibility we have to keep in mind. In many, many countries security incidents are created only for the purpose of demonstrating that this or that force is indispensable."

Violence has worsened ahead of the elections, despite the presence of more than 20,000 U.S.-led troops hunting Taliban and al-Qaeda guerrillas, and 6,500 NATO-led peacekeepers.

NATO has agreed to send 1,500 more troops to Kabul and to the relatively stable north for the polls -- far fewer than the United Nations and the government had been seeking. Arnault said the violence showed the need for more troops, now.

"Protection of the election process is not a matter of arriving for polling day," he said. "The time for the arrival of international forces is now, not in four months from now."