An elderly man wounded by a bomb in a western Afghan city died overnight, a city health official said Monday, lifting to six the toll from a blast that underlined the fragile security this nation still faces less than three months before presidential elections.

A suspect arrested in the wake of Sunday's rush-hour explosion in Herat's Old City led authorities to three more people wanted for questioning in the blast, deputy intelligence chief Abdul Wahid Tawaqali (search) told The Associated Press.

It remained unclear whether militants trying to disrupt the Oct. 9 presidential vote, or factions loyal to powerful regional warlords were behind the attack.

The United Nations has been pushing for the disarmament of tens of thousands of local militia fighters.

In an interview in Monday's New York Times, President Hamid Karzai (search) reiterated his view that abusive militias and criminals are more of a threat than the Taliban.

Herat saw one of the worst bursts of factional fighting in March. Sixteen people died, including a Cabinet minister and a son of Gov. Ismail Khan (search).

Karzai didn't refer in the interview to Khan, an anti-Taliban and anti-Soviet resistance leader who the United Nations has accused of stalling efforts to disarm his private army.

But he indicated that a tougher approach was needed on disarmament.

"We tried to do it by persuasion," Karzai was quoted as saying. "The stick has to be used, definitely."

Herat's public health chief, Mohammed Omar Sameem, said an elderly man died of his wounds in a city hospital. Three other men and two children died earlier.

Of 34 others injured, seven were still in hospital Monday while relatives took six others to Iran for treatment, Sameem said.

Police seized a man Sunday suspected of involvement in the blast and found pistols and ammunition in his home.

Tawaqali said the suspect pointed them toward three other suspects, all from the southern city of Kandahar, but police said no one else had been arrested.

"We still don't have any evidence" if any militant group or faction was behind the attack, he said.

Karzai blamed enemies of peace and democracy for the blast, which came amid a wave of violence that has killed nearly 600 people across the country this year.

Khan, who warned that demobilizing his men could leave a security vacuum, stayed away from a ceremony on Sunday in Herat where 750 militiamen set for demobilization paraded for the last time.

Afghanistan's electoral commission cited slow disarmament in its decision Friday to postpone parliamentary elections, originally to be held along with the presidential vote, but now set for April.

The United Nations is concerned that factions will use their guns and wealth to fill parliament with their supporters, and hopes that most of the militias will have disappeared by April.