The Taliban have killed 17 civilians – reportedly by cutting their throats – in a remote and violent corner of Afghanistan's Helmand province that government officials admit is entirely beyond their control.

The reason for the slaughter was variously given as a fight between two Taliban commanders over women, Taliban anger over a music and dance party, or an insurgent crackdown on suspected government informers.

The group, which included two women, were killed early on Sunday afternoon but news of their deaths only reached government-held areas on Monday.

"This happened in a desert area known as Roshanabad, which is not under the control of the government," said the Kajaki district governor, Mullah Sharafuddin, who said he did not know the motive behind the attack. "I am the governor but I don't have full details because this land is under Taliban control."

The Helmand police commander's office said it had been told the 17 victims were targeted as government spies.. The provincial governor's spokesman, Daoud Ahmadi, said the dead were probably caught up in a fight between two rival Taliban commanders for control of the dead women.

"There are two Taliban commanders, Mullah Wali Mohammad and Mullah Sayed Gul, that control the area near Kajaki, but they argued about the two women," Ahmadi said. "We don't know exactly what the differences are, but the killing was because of the difference between the two commanders over these women. Their throats were slit but their heads were not completely cut off."

The president, Hamid Karzai, blamed the Taliban and ordered a full investigation. "This attack shows that there are irresponsible members among the Taliban," he said.

Earlier reports said the group were beheaded because they had attended a party that insurgents considered immoral. "The victims threw a late-night dance and music party when the Taliban attacked," the Reuters news agency quoted the governor of nearby Musa Qala district as saying.

The Taliban could not be reached for comment. There is a precedent for killings of civilians in quarrels driven by passion and jealousy in Afghanistan. On New Year's Day in 2010, six civilians were beheaded in Uruzgan province. The killings were initially reported as a Taliban attack on alleged government spies, but it later emerged they were the result of two groups fighting over a boy.

This summer a woman was stoned to death in Parwan province in what was thought to be Taliban punishment for adultery. Parwan's governor later said she was involved with a commander who killed her to avoid losing face as news spread of his behaviour.

The killings on Sunday came at the start of a bloody 24 hours in which 10 Afghan soldiers were killed in a nearby district by a Taliban assault, and Afghan army soldiers shot dead two Nato troops in the east.

The Afghan soldiers died in an attack on a checkpoint in a violent part of Washir district. Eleven Taliban were also killed and some soldiers fled the onslaught, but the government has held the checkpoint.

"Two weeks ago the Taliban attacked the same checkpost, five soldiers were killed but they didn't manage to take the checkpost," said Ahmadi, the governor's spokesman. "Last night it was similar, although 10 soldiers were killed, but the Taliban couldn't take control."

The two foreign troops were killed during an operation in eastern Laghman province, where there are no Nato bases because security control has been handed over to Afghans. The shooting brings the number of foreign troops who have died at the hands of their Afghan allies this month to 12.

Mokhtar Amiri contributed reporting