Six NATO soldiers, including three US service members were killed in a series of clashes with insurgents and roadside bombing on Monday, the military alliance said, DPA reported.
The three US soldiers died on Monday afternoon "in an engagement with enemy forces in southern Afghanistan," NATO-led International Security Assistance Force said in statement.
The statement did not identify the soldiers, nor did it say where in the south the incident occurred. Most of the American troops are stationed in volatile Kandahar and Helmand provinces.
Two other NATO soldiers were killed in a fight with the insurgents in eastern region, NATO said in a separate statement. It did not disclose the soldiers' nationalities, but French Defence Ministry reportedly said the deceased soldiers were from France.
The sixth NATO soldier was killed in a roadside bomb blast also on Monday in southern region, ISAF statement said, but did not reveal soldier's nationality. Most of the forces based in the region are from Canada, Britain, Netherlands and the US.
Fifteen NATO soldiers, including at least ten US troops have been killed in Afghan conflict so far in January, a bloody start to the New Year.
A total of 520 international troops, including 317 US soldiers, were killed in Afghanistan last year, the deadliest period for US and NATO forces since the ouster of Taliban regime in late 2001.
More than 110,000 foreign troops are currently stationed in Afghanistan. Up to 37,000 additional US and NATO troops are expected to arrive in the summer as part of a military escalation against the Taliban insurgents who are more effective than ever.
In southern province of Helmand, Afghan and NATO troops killed 11 Taliban fighters and wounded nine others in an operation in Musa Qala district on Sunday, the Afghan Defence Ministry said Monday.
There were no casualties among the combined forces, it said.
A NATO helicopter was damaged in a "hard landing" in Helmand province on Monday, but caused no casualties among the crew members aboard, a military statement said.
President Hamid Karzai paid tribute on Monday to Rupert Hamer, a British journalist with the Sunday Mirror newspaper, who was killed along with a US Marine and an Afghan soldier in a roadside bomb attack in Helmand province on Saturday, the government said.
Karzai praised the Hamer for his courage in "trying to cover the real situation on the ground".
Hamer's photographer and four US Marines were seriously wounded in the attack.
The Defence Ministry said government troops and NATO forces agreed to transfer responsibility of a US-run prison at Bagram military base to the Afghan army within the next few months.
Ministry spokesman General Zahir Azimi said a military unit would be trained to run the facility before the transition is made.
More than 700 prisoners, mostly Taliban insurgents, are currently held in the Bagram prison.