Afghan security forces appear to be close to quelling a wave of Taliban attacks in which several people died during a second day of violence in one of Afghanistan's biggest cities.

At least 22 people, including 18 fighters, have been killed in Kandahar city, according to the governor of Kandahar province.

Two attackers who were holed up in a building near Kandahar's intelligence headquarters are dead, leaving just one more inside, Zalmay Ayoubi, a provincial spokesman, told the AFP news agency.

"Two attackers were shot dead. There is one person still in there," he said.

"Eight vehicles packed with explosives were found today and destroyed by foreign forces. One suicide bomber driving a car was identified, shot at and killed by Afghan security forces."

Kandahar's streets were said to be virtually deserted on Sunday, while roads into the city have been blocked off.

Kandahar city is the birthplace of the Taliban and the economic hub of southern Afghanistan.

Major assault

Taliban forces unleashed a major assault on Saturday on government buildings, including the intelligence agency headquarters and a police station.

NATO troops and helicopters could be seen supporting Afghan forces in the clash.

Fighting had temporarily stopped overnight after Afghan forces had secured the government buildings which had been attacked.

Of the dead attackers, eight were reported to have detonated their suicide vests, while four fighters were said to have been captured.

The size and scope of the assault, which began at noon, cast doubt on the effectiveness of a year-long campaign to secure Afghanistan's south and Kandahar in particular.

The Taliban claimed more than 100 fighters took part and said its goal was to take control of the city.

It was the most ambitious attack since the fighters declared the start of a spring offensive last month against NATO and Afghan troops.

Nearly all the fighters are believed to have escaped late last month from Kandahar city's main Sarposa prison.

More than 480 Taliban members escaped through a 300-metre long tunnel that took five months to dig.

The Kandahar assault is the latest in an ongoing series of attacks by the Taliban on prominent government installations.

Al-Qaeda 'revenge'

A statement from the office of Hamid Karzai, the Afghan president, on Saturday said the attacks were revenge for the recent killing of al-Qaeda's leader by US forces.

"Al-Qaeda and its terrorist members who have suffered a major defeat with the killing of Osama bin Laden in Pakistani territory have tried to hide this defeat by killing civilians in Kandahar and take their revenge on the innocent people of Afghanistan," the statement said.

The Taliban issued a statement on Friday saying that the killing would boost the morale of the group, and threatening that it would show its strength.

"The martyrdom of Sheik Osama bin Laden will give a new impetus to the current jihad against the invaders," the Taliban said.

"The forthcoming time will prove this both for the friends and the foes."

However, Qari Yousef Ahmadi, a Taliban spokesman, told the AP news agency on Saturday that the Kandahar assault was not a revenge attack for bin Laden's death but a plot that had been in the works for months.

"This operation has been planned for a long time, for the past month or two," he said.

Source: Al Jazeera and agencies