Explosions and sporadic gunfire rocked the outskirts of Ghazni Tuesday after the Taliban attempted to storm the southeastern city, as the insurgents tighten their grip across Afghanistan following their lightning capture of another provincial capital.

Afghan forces repelled the brazen assault on Monday, but it rang security alarm bells as the largely rural insurgency threatens large cities for the first time in 14 years of war.

Taliban insurgents in military uniform stormed an Afghan prison Monday, freeing hundreds of inmates after detonating a car bomb and killing four policemen in the country's largest jailbreak in years.

The brazen raid in the eastern city of Ghazni comes as the Taliban ramp up attacks on government and foreign targets despite being embroiled in a bitter leadership transition.

A suicide bomber on a bicycle attacked a police checkpost in southeast Afghanistan on Saturday, killing at least two civilians and wounding five others, provincial authorities said.

"Two civilians were killed and five others are wounded in an explosion outside police security checkpost in the city of Ghazni today afternoon," said Mohammad Hasan, security chief for police in Ghazni, about 150 kilometers (93 miles) from the capital Kabul.

Two Afghan policemen were killed and three wounded when NATO-led forces shot them at a checkpoint, a local police chief said Saturday.

The incident happened due to a "misunderstanding" between international troops and the Afghan forces, who are jointly fighting a ten-year Taliban-led insurgency in Afghanistan, the chief added.

Six Afghan police were killed Wednesday when Taliban attacked their checkpoint, a brazen assault likely to raise fresh security questions as the United States prepares a troop draw down.

The Taliban, which is leading a nearly 10-year war against the Afghan government and U.S.-led foreign troops, claimed responsibility for the attack in Qarabagh district about 120 kilometers southwest of Kabul.