(CNN) 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.

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