A suicide bomber struck near a police convoy in eastern Afghanistan on Wednesday, killing five people and wounding 38 in the latest in a growing wave of Iraq-style homicide attacks, while a huge, accidental explosion at a Kabul gunpowder shop cost six lives.

The attacker, described as a young man wearing a Muslim prayer cap and a shawl, detonated his explosives as the last in a column of police vehicles passed in front of a bank on a busy shopping street in Khost, a city close to the Pakistani border, officials and witnesses said.

Four civilians and a policeman were killed, according to Gul Mohammadin Mohammadi, the provincial health chief. Nine of the 38 wounded were policemen, but most were shopkeepers and pedestrians, Mohammadi said. Twelve of those hurt were in critical condition.

Homicide attacks have become a key weapon for Taliban insurgents who made 2006 the bloodiest year in Afghanistan since U.S. forces drove the hard-line militia from power in late 2001. The tactic has put NATO and U.S. troops on edge, resulting in a string of deadly shootings of civilians.

In the latest incident, NATO said its forces in Kandahar fired at a truck that came too close to their convoy Wednesday, killing the driver.

Afghan and western officials have pleaded with foreign forces to use caution to prevent civilian casualties. NATO and U.S.-led coalition forces have now shot at least 10 people who have driven close to their convoys since January, according to an Associated Press tally.

In other violence, suspected Taliban fighters attacked a police checkpoint near Qalat in the southern province of Zabul early Wednesday. The ensuing gunbattle left a policeman wounded, said Zabul highway police commander Ghulam Jailali. Two militants were arrested.

In a similar incident, Kandahar provincial police chief Esmatullah Alizai said two police were killed and one wounded in a gun battle that followed a Taliban attack on a checkpoint Tuesday night on the Spin Boldak-Kandahar highway.

As well as the risk of getting caught up in the insurgency, Afghans have to contend with the absence of safety standards in a country awash with weapons and explosives.

Residents in the capital were awoken early Wednesday by a huge blast at a gunpowder store in central Kabul that destroyed dozens of shops and houses, killed at least six people and wounded nine, officials said.

Deputy city police chief Zulmay Khan said gunpowder in shops selling ammunition for hunting rifles had exploded. It is unclear what ignited the gunpowder.

The blast gouged a huge crater out of the neighborhood, threw piles of burning wreckage into the street and shattered windows for hundreds of meters (yards) around.

The incident evoked the May 2005 detonation of a huge cache of explosives and ammunition stored under a warlord's house in northern Afghanistan that destroyed half of a village and killed at least 25 people.