The Afghan government has concerns about the draft peace agreement reached between US and Taliban negotiators and wants further clarification, President Ashraf Ghani's main spokesman said on Wednesday.

The deal, which would see around 5,000 US troops withdrawn and five bases closed in exchange for guarantees that Afghanistan would not be used as a base for militant attacks on America, was presented to Ghani this week by the special US envoy for peace in Afghanistan, Zalmay Khalilzad.

However, with the Taliban stepping up attacks in the capital Kabul and provincial centres across the country, the agreement has faced scepticism from several sides, including a number of former US officials and politicians.

"The Afghan government is also concerned and we, therefore, would like further clarity on this document to completely analyse its dangers and negative consequences and avoid the dangers," Ghani's spokesman, Sediq Sediqqi, wrote on Twitter.

Many officials in the Afghan government, which has been shut out of the talks by the Taliban's refusal to talk to what they consider a foreign-imposed "puppet" regime, have been deeply concerned a deal will give too much and allow the Taliban back into power.

In recent days, large groups of insurgent fighters have attacked the northern cities of Kunduz and Pul-e Khumri. The Taliban also claimed responsibility for a large tractor-bomb attack on a heavily protected compound used by foreign organizations in Kabul on Monday night.

On Wednesday, heavy clashes were reported in Takhar and Sar-e Pul in northern Afghanistan, as well as continuing fighting in Pul-Khumri. In the southern province of Uruzgan, a car bomb attack on the police headquarters in Khas Uruzgan district was followed by a fierce gunbattle, while in the eastern province of Paktia, a district police chief was killed by a roadside bomb.

Khalilzad is expected to hold a series of meetings with Afghan and NATO officials to explain the draft agreement, which must still be approved by U.S. President Donald Trump before it can be signed.

The deal, reached after months of negotiations, is intended to open the way for so-called "intra Afghan" talks to end the fighting and reach a full political settlement. However, deep suspicions remain and it is still unclear whether the Taliban will agree to full talks with the government.

Previously, the Taliban have said they were willing to meet government officials purely in a personal capacity and not as representatives of the state.