KANDAHAR, Afghanistan (Reuters) - A blast in the southern Afghan city of Kandahar on Tuesday caused dozens of casualties, officials said, as fighting across the country showed no sign of easing off during the Muslim holy month of Ramadan.

There was some confusion about the cause of the Kandahar explosion, which sent a huge cloud of dust and smoke into the air. Officials initially said it was caused by a bomb packed into a minibus but later said the explosives were in two containers stored in an area of mechanics workshops.

Nematullah Barak, a head of the Mirwais hospital in Kandahar, said 16 dead and 38 wounded, including several children, had been brought in but the final total could be higher as ambulances were still at the scene.

The NDS intelligence service said in a statement the explosives were discovered in a large open yard of workshops but went off before they could be defused.

There was no immediate claim of responsibility.

Witnesses said repair crews were at the site, clearing large quantities of rubble and debris from the explosion.

The casualties add to the hundreds of people who have been killed or wounded in bomb attacks since the beginning of the year.

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Many have been in the capital, Kabul, but provincial cities have also been hit as the Taliban, seeking to reimpose hardline Islamic rule, have stepped up fighting across the country.

Kandahar province, on the border with Pakistan, is a major center of opium cultivation and a stronghold of the Taliban but the city has recently been relatively secure.

Tuesday’s explosion came as the Taliban pushed ahead with their spring offensive, launched last month, with fighting in several areas of the country.

As many as seven police were killed in clashes on Monday night between security forces and the Taliban in Ghazni province, southwest of Kabul, where the insurgents have cut a highway with the neighboring province of Paktika, officials said.

Arif Noori, spokesman for the provincial governor, said a large Taliban force attacked government positions in five districts of the province late on Monday, with fighting continuing until dawn.

Insurgents burned down the police headquarters in Jaghato district, he said.

The latest fighting coincided with a U.S. government report that found few signs of progress this year, with fighting spreading and hundreds of casualties from militant attacks.

Security officials say violence is expected to pick up as preparations continue for parliamentary elections scheduled for October.