Ghazni, Afghanistan: Taliban insurgents in military uniform set off a car bomb and stormed an Afghan prison Monday, freeing hundreds of inmates and killing four policemen as they step up attacks despite a bitter leadership transition.

The brazen attack in the eastern city of Ghazni was reminiscent of the last major Afghan jailbreak in 2011 when nearly 500 Taliban inmates escaped from a prison in the southern province of Kandahar.

The raid, which left bullet-riddled bodies at the entrance of the prison, comes as Afghan forces face their first fighting season against the insurgents without full NATO support.

‘Around 2:30 am six Taliban insurgents wearing military uniforms attacked Ghazni prison. First they detonated a car bomb in front of the gate, fired an RPG (rocket-propelled grenade) and then raided the prison,’ deputy provincial governor Mohammad Ali Ahmadi told AFP.

The interior ministry said 355 of the prison's 436 inmates  escaped. Most were charged with crimes against national security and other criminal offences.

It added that four Afghan police officers were killed and seven wounded.

The Taliban, who launched a countrywide summer offensive in late April, claimed responsibility.

‘This successful operation was carried out at 2:00 am and continued for several hours. The jail was under Taliban control,’ spokesman Zabihullah Mujahid said in a statement.

‘In this operation, 400 of our innocent countrymen were freed... and were taken to mujahideen-controlled areas,’ it added.

The Taliban are known to exaggerate and distort their public statements.

In 2011 almost 500 Taliban fighters and commanders escaped from a prison in an audacious jailbreak in Kandahar province, in what the government described as a security ‘disaster’.

The Taliban at the time said they sprang the inmates through a one-kilometre tunnel that took five months to dig.

- Uptick in attacks –

Taliban insurgents are stepping up their summer offensive despite a simmering leadership succession dispute after the confirmation of the death of longtime chief Mullah Omar.

Mullah Akhtar Mansour, a trusted deputy of Omar, was named as the insurgents' new chief in late July, but the power transition has been acrimonious.

Afghan security forces, stretched on multiple fronts, are struggling to rein in the Taliban as NATO forces pull back from the frontlines.

NATO ended its combat mission last December and pulled out the bulk of its troops although a 13,000-strong residual force remains for training and counter-terrorism operations.

In other bloodshed this month unidentified attackers on September 5 shot dead 13 minority Shiite Hazaras after dragging them out of their vehicles in the northern province of Balkh.

The men were taken from two vehicles in a rare fatal attack targeting ethnic minorities.

Afghanistan's president the same day implored international donors  for their continued support, saying the ‘wounded country’ faced a host of security and economic challenges.

Donors have pledged billions of dollars over the past decade to reconstruct the war-torn country.

But much of that money has been lost to corruption, which permeates nearly every public institution, hobbling development and sapping already overstretched state coffers.