The soldier was killed in the southern Helmand province, a NATO statement said. It did not provide details on the clash or give the soldier's nationality.
Separately, another NATO soldier and six Afghan troops were wounded when mortars hit their base in neighboring Kandahar province early Sunday, the statement said. The soldiers were evacuated to a military medical facility for treatment.
Meanwhile, a large number of militants attacked the Musa Qala district compound in Helmand on Saturday, sparking a clash with police that left 10 insurgents dead, said Ghulam Nabi Malakheil, provincial police chief.
The militants left the dead bodies alongside seven AK-47 assault rifles, five rocket-propelled grenades and two heavy machine guns, he said. There were no police casualties.
On Sunday, attackers fired four rockets targeting west Kabul, said district police chief Gen. Zalmai Oryakail. One landed near the district police station but injured no one, and another one damaged a house, he said.
Kabul has been spared most of the violence that has engulfed Afghanistan's south and east, but a series of bombings and attacks on NATO-led peacekeepers has rattled the nerves of its citizens.
Afghanistan is experiencing its worst violence since the late-2001 ouster of the Taliban regime for hosting al Qaeda leader Osama bin Laden. More than 1,600 people, mostly militants, have died in the past four months, according to an Associated Press tally of violent incidents reported by U.S., NATO and Afghan officials.
Armed men ambushed a bus transferring 30 prisoners from Kandahar to Kabul on Sunday, killing one prison official and wounding one policeman, said Noor Mohammad Paktin, police chief of Zabul province.
After escaping briefly following the attack in southern Zabul province, police and soldiers managed to capture all those that fled and took them to Kabul, Paktin said. It was not clear who the prisoners were.
Meanwhile Gen. John Abizaid, the commander of the U.S. Central Command, said "it is clear" that militants are using Pakistan to infiltrate Afghanistan.
"I think that Pakistan has done an awful lot in going after al Qaeda, and it's important that they don't let the Taliban groups be organized in the Pakistani side of the border," Abizaid told reporters in Bagram, site of the main U.S. military base in Afghanistan.
However, Abizaid said he "absolutely does not believe" accusations of collusion between Pakistan's government and the resurgent Taliban rebels or other extremists.
Afghanistan has repeatedly criticized Pakistan for not doing enough to prevent Taliban militants and other rebels crossing the poorly marked border.
Pakistan, a former Taliban supporter but now a U.S. ally in its war on terrorism, says it does all it can to tackle insurgents and has deployed 80,000 troops along the frontier.
On Saturday, Canadian troops mistakenly killed a policeman and wounded six other people, including four other police, a NATO statement said.
The armed plainclothes police were shot after they did not heed troops' orders to stop as they approached a Canadian checkpoint in a speeding, unmarked vehicle in Kandahar province's Zhari district, the statement said.
Two other civilians were injured later when the Canadian troops fired at their speeding scooter near the same checkpoint, the statement said. No Canadian troops were reported injured.
Afghan officials were not immediately available for comment.