KABUL, Afghanistan - Three Taliban attacks killed at least 19 people in Afghanistan on Saturday, including a senior judicial official and personnel working to clear one of the most heavily mined regions of the world.

The attacks came amid a spike in violence just weeks before the international military mission in Afghanistan comes to an end on Dec. 31., 13 years after the Sept. 11 attacks sparked a U.S.-led invasion to rid Afghanistan of the Taliban's extremist regime.

As the Taliban insurgency vows to maintain its current campaign against government, military and foreign targets, the attacks have sparked tight security in Kabul and concerns among Afghans that the situation can only worsen after foreign forces have transitioned to a support role from Jan. 1.

The U.S. and NATO will leave around 13,000 troops in the country, with sliding reductions over the coming two years. With the end of NATO's International Security Assistance Force, the residual troops are meant to offer training and support to Afghan security forces that have been leading the anti-insurgency fight while suffering record casualties since the middle of last year.

President Ashraf Ghani made it clear during recent overseas trips that he believes Afghanistan needs ongoing financial and military support as the insurgency intensifies and spreads.

The Taliban claimed responsibility for the Saturday attacks, as well as one late Friday in which two American soldiers were killed, according to an international military official who spoke to the Associated Press on condition of anonymity as the information wasn't authorized for release. The soldiers died when a suicide bomber targeted their convoy near the Bagram air base, outside Kabul.

Their deaths took to 65 the total number of international troops to die in Afghanistan this year, 50 of them Americans. In all, 3,500 foreign forces, including at least 2,210 American soldiers, have been killed since the war began in 2001. By comparison, Afghan security casualties spiked 6.5 percent this year, with 4,634 killed in action by the end of September.

Maj. Gen. Afzal Aman, chief of operations at the Defense Ministry, said that six Afghan soldiers died when a suicide bomber attacked a bus taking them home late Saturday afternoon. He said the attack was most likely carried out by a suicide bomber on foot. Eyewitnesses said the bus was destroyed by fire.

Early Saturday, gunmen shot dead Atiqullah Rawoofi, the head of the court's secretariat in Kabul's northwestern suburbs, said Farid Afzali, chief of the Kabul police criminal investigation unit. Rawoofi was walking from his home to his car on his way to work when he was shot dead by militants, he said.

Hours later Taliban fighters shot dead at least 12 workers clearing mines in southern Afghanistan, authorities said.

Police identified the company working on the project as Star Link. An employee of Star Link, who spoke on condition of anonymity as he was not authorized to speak to journalists, said the number of dead could be higher.

Afghanistan, which has suffered decades of continuous war, is one of the most heavily mined countries in the world. The nonprofit Halo Trust estimates 640,000 mines have been laid there since 1979 and at least 20,500 people have been killed and wounded by such ordinance since.