A U.S military official told Reuters on Friday night that dozens had been killed in an attack on an Afghan military base in Mazar-e-Sharif in Balkh province, but local officials said the death toll was eight.

"We're talking probably more than 50 casualties," said Colonel John Thomas, a spokesman for the U.S. military's Central Command, as quoted by Reuters.

"There is a mosque and a dining facility on the base that seemed to, at this point from our reports, be the subject of significant attack from enemy forces," he was quoted as saying.

Dawlat Waziri, a ministry of defense spokesman said insurgents wearing army uniforms stormed a military compound in Afghanistan’s northern Balkh province during Friday prayers.

He said the militants entered the building with a military vehicle and began shooting at the soldiers as they prayed in the compound’s mosque.

Officials said six insurgents penetrated multiple layers of security barriers and launched the attack inside the Afghan National Army’s 209 Shaheen Corps Headquarters in Balkh province at about 1.30pm.

The siege lasted for five hours said officials. Five insurgents were reportedly killed and the sixth arrested.

The attack happed just two days after Interior Minister Taj Mohammad Jahid visited the base during a trip to Balkh.

He said at the time there were no good terrorists or bad terrorists but that any person or group that fights government forces with the intention of destabilizing the country are enemies of Afghanistan.

“Government’s resolve is indeed strict against insurgents. Government’s resolve is to support the security and defense forces and government’s will is indeed to bring peace and stability to the country,” he said.

However, Balkh Governor Atta Mohammad Noor said the same day he is concerned about the spread of insecurity in the northern provinces and that it would increase if security forces do not take an offensive stance against militants.

“Do not let insurgents infiltrate, strengthen and create problems for us. If we let them collect (illegal) taxes, cultivate poppies and conduct smuggling, they will receive money and will further equip [their fighters]. Then they will manage more wars,” Noor said.

Friday’s attack meanwhile is the second serious attack on a military installation in recent months. 

Two months ago, insurgents attacked the Sardar Mohammad Daoud military hospital in Kabul killing at least 50 people. 

This attack drew widespread condemnation at the time, with the Wolesi Jirga (lower house of parliament) severely criticizing government over its failure to prevent such an attack, saying such attacks on highly-secured compounds "shame the government".