A suicide bomber wearing an army uniform blew up an Afghan military bus in Kabul Saturday, killing around 30 people and wounding many more in one of the deadliest attacks of the Taliban's insurgency.

Afghanistan's US-backed president, Hamid Karzai, called for "stronger vigour" in the worldwide fight against terrorism after the devastating blast.

Comment: How do they know that it was a suicide bomber? Remember any one including the Western counterinsurgency can make a phone call and claim to be a spokesman calling on behalf of the Taliban.

The attacker detonated his explosives at the entrance of the bus as it picked up army personnel going to work at the defence ministry in the centre of the heavily guarded city, ministry spokesman General Zahir Azimi said.

The force of the explosion blew off the roof and sides of the large bus, which was torn into mangled metal.

Television pictures showed rescuers rushing bloodied bodies from the vehicle. Some of the dead were still in their seats. Debris was scattered across a wide area. Around 30 people were wounded.

The extremist Taliban movement claimed responsibility for the morning rush-hour attack, which was the deadliest in the city since a similar explosion on a police bus in June killed about 35 people.

In the immediate aftermath, officials had different casualty tolls: Karzai said 28 military personnel and two civilians were killed.

Public Health Minister Sayed Mohammad Amin Fatemi said 31 were dead, nearly all military, and 17 critically wounded, while the interior ministry said 27 were dead and 29 wounded.

Taliban spokesman Zabihullah Mujahed said the attack was part of a Taliban "operation" planned for the Islamic holy month of Ramadan.

There have been more than 100 suicide blasts in Afghanistan this year, most blamed on the Taliban movement which was driven from government by a US-led coalition in late 2001 after seizing power five years earlier.

While most insurgency-linked attacks are in remote areas in the south and east of Afghanistan, there have been a series of strikes inside Kabul this year.

The last was a suicide bomb on September 21 that struck a NATO armoured vehicle, killing a French soldier and wounding several Afghans.

The deadliest was on a police bus on June 17. Officials said at the time that 35 policemen were killed, making it the worst such attack since the Taliban launched its insurgency.

Karzai strongly condemned Saturday's attack at a media briefing hours after the explosion.

It "is something that would indicate to us that the war against terrorism must go on with much stronger vigour," the grim-faced president told reporters at his palace.

"From Algeria to Indonesia, from the United States to Japan, we all have to keep together and remain steadfast in the war against terrorism," he said.

He said the attack was "against humanity, definitely against Islam."

"A man that calls himself Muslim would not blow up innocent people in the month of Ramadan," he said.

Comment: Exactly!

The UN special representative Tom Koenigs said the attack was among the worst Kabul had ever seen.

"An attack of this kind, on a busy city street, clearly aims at terrorising large numbers of people. Society must stand firm in its condemnation of such acts," he said in a statement.

The Taliban was ousted from government in a US-led invasion launched weeks after the 9/11 attacks blamed on Al-Qaeda, which was sheltered by the Taliban government.

They took Kabul in September 1996, ending a civil war but imposing an austere version of Islam on the battered country.

The rebels' insurgency has grown steadily, with almost daily attacks in the south and east.

The violence has killed more than 5,000 people this year, most of them rebels but including more than 700 civilians and 600 Afghan security forces.

More than 175 of the roughly 50,000 mostly Western soldiers in the country to help the fragile Afghan government assert its authority have also been killed, most of them fighting Taliban and other insurgents.