Sixteen civilians, mostly women and children, were killed by a U.S. soldier and five others were injured on Sunday in two incidents in southern Afghan province of Kandahar.

16 civilians were killed and five others were injured on Sunday in two incidents in southern Afghan province of Kandahar.

Sixteen civilians, including four men, three women and nine children, were killed Sunday when a U.S. soldier with the NATO- led International Security Assistance Force (ISAF) walked out from a military base and begun shooting on civilians in Najibyan village of Kandahar's Panjwayi district, according to a witness namely Halim Sadozai.

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Meantime, the NATO-led ISAF confirmed that a U.S. service member with ISAF was detained on charge of inflicting casualties on civilians in Kandahar province, some 450 km south of capital Kabul.

"A United States service member was detained today in connection to an incident that resulted in Afghan casualties in Kandahar province," the ISAF said in a press release issued here.

"U.S. Forces-Afghanistan (USFOR-A), in cooperation with Afghan authorities, will investigate this incident and release additional information as appropriate," the ISAF press release said.

"This is a deeply regrettable incident and we extend our thoughts and concerns to the families involved," the ISAF said in the press release.

Earlier Sunday, Kandahar provincial governor Toryali Weesa told a press briefing that a U.S. soldier opened fire on civilians in the wee hours Sunday in Zand Abad areas of the district leaving several civilians dead or injured.

An investigation was launched into the incident, Weesa said, adding that more details will be released to media after investigation.

Afghan Interior Ministry officials were not immediately to make comments.

The motive behind the attack was not clear so far.

Seven other civilians were killed during a military operation launched by U.S. Special Forces of ISAF in Barakzai area of Panjwayi district also on Sunday morning, according to local media.

The deaths of Afghan civilians by NATO-led troops during operations against Taliban have long been a contentious issue between the Afghan government and U.S. and NATO forces in the country.

A total of 3,021 Afghan civilians were killed in 2011, according to a UN annual report released in Kabul on Feb. 4.

The UN report attributed 77 percent of the civilian deaths last year to the attacks of Taliban insurgents and other armed groups opposing the Afghan government.