Kabul — U.S. envoy Zalmay Khalilzad has returned to Qatar for more, unscheduled talks with the Taliban. His return comes just four days after Khalilzad announced that his team had reached an agreement "in principle" with the Taliban aimed at ending the longest war ever to ensnare the U.S. military.

When he announced the draft agreement on Monday, Khalilzad said his negotiations with the extremist group had concluded and that the deal lacked only approval from his bosses in the Trump administration.

The U.S. envoy's team would not elaborate Friday on the nature of the resumed discussions in Doha, but they come after a series of deadly Taliban attacks across Afghanistan. As CBS News correspondent Charlie D'Agata reports, while the Taliban may be talking peace with the U.S., they're still waging a brutal war on Afghan soil.

A security camera captured dramatic video of a car bomb attack in Kabul on Thursday. The blast near the U.S. Embassy killed one American service member and another NATO soldier, as well as at least 10 civilians.

Sixteen U.S. troops have been killed in Afghanistan this year, three of them in just the past couple weeks.

The government in Kabul has been completely side-lined from the talks between the U.S. and the Taliban in Doha - to the extent that President Ashraf Ghani was shown a copy of the deal, but not allowed to keep it.

Taliban representatives insisted to CBS News on Friday morning that the attacks were justified, in order to give them a stronger position in the negotiations with the U.S., and they said the violence would continue.