Afghan security forces are engaged in intense fighting with Taliban militants in Ghazni, three days after the start of an offensive on the strategic city that has so far killed more than 150 people, according to a local member of parliament.

Mohammad Arif Shahjahan, an MP from Ghazni, told CNN Monday Taliban fighters had taken control of key buildings, including the police headquarters and some government offices.

Many of the dead were security forces, he said, adding that many more had been injured, as fighting continued into its fourth day, despite government and US assurances that the assault had failed.

Taliban militants stormed the strategically important city Friday in an attempt to establish a base within easy access of the capital Kabul to the north, and roads to western and some southern provinces.

The move perhaps the most serious challenge to the government's hold in urban areas since the Taliban briefly occupied the city of Kunduz in 2015, and comes at a time when the Trump administration appears to be accelerating negotiations with an insurgency it has been fighting for 17 years.

According to a tweet from Afghanistan's Interior Ministry Sunday, Ghazni police had started a planned clearance operation in the city, in an attempt to push the militants out.

Afghan President Ashraf Ghani said on his official Twitter account Sunday that he had chaired an emergency meeting to discuss the situation in Ghazni Province, and it was determined that further back-up was needed.

"After detailed review of the reports, the meeting decided that in order to consolidate operational gains, further reinforcements should be dispatched to the province on urgent basis," Ghani said.

There were reports of sporadic fighting over the weekend, but a spokesman for the Afghan National Army said Saturday the city was "under the complete control of Afghan security forces."

"Afghan National Army reinforcements are making their way to Ghazni city to help the Afghan National Police search and clear the city of insurgents that may still be hiding in the city," said Maj. Mohammad Farooq, an Afghan National Army 203rd Corps spokesman. (CNN)

•Smoke is seen rising into the air after Taliban militants launched an attack on the Afghan provincial capital of Ghazni on Friday.