Askar blamed the blast on Taliban fighters who have been waging a bloody insurgency since they were ousted from power during the US-led invasion nearly nine years ago.

Suicide attack

In November 2009, 13 prisoners escaped from the same prison via a tunnel and in June earlier that year, at least to 1,000 Taliban inmates escaped from Sarpoza prison in Kandahar city after a suicide attack blew open the front gates and destroyed the walls.

Sunday's prison break comes just two days before Afghanistan is due to host a major international donors conference, set to be attended by up to 40 foreign ministers, including US secretary of state Hillary Clinton.

But Zemarai Bashary, a spokesman for the interior ministry, said thousands of police officers, soldiers and intelligence agents had been deployed "in vulnerable areas" of the Afghan capital, Kabul, as well as remote villages to thwart any Taliban attack plans.