Taliban insurgents dressed in police uniforms killed up to 15 policemen after raiding a security checkpoint in southern Afghanistan

Taliban insurgents dressed in police uniforms killed up to 15 policemen after raiding a security checkpoint in southern Afghanistan, officials said Wednesday, in the latest attack of their intensifying summer offensive.

The attack on Tuesday in Musa Qala district in the volatile province of Helmand highlights an expanding insurgency that has left beleaguered Afghan forces stretched on multiple fronts.

"At least nine policemen were killed after insurgents disguised in police uniforms attacked a check post in Musa Qala district," said Omar Zwak, spokesman for the governor of Helmand.

But Bashir Shakir, a member of the provincial council, gave a higher toll, saying 15 policemen were killed in the late night attack.

Taliban spokesman Qari Yusouf Ahmadi claimed responsibility for the raid.

The Taliban are stepping up their summer offensive, launched in late April, amid a bitter leadership dispute following the announcement of the death of longtime supremo Mullah Omar.

A wave of bombings since last Friday in the capital Kabul have killed at least 56 people and wounded hundreds, prompting fury from President Ashraf Ghani who blamed Pakistan for failing to rein in the Taliban.

Observers say the new upsurge in violence represents a bid by new Taliban leader Mullah Akhtar Mansour to distract attention from the crisis roiling the militant movement.