Twelve youths were killed following a raid on a house in the eastern Turkish city of Van.

The raid was carried out in Van's central Edremit district by a Turkish special operations team early on Sunday.

A statement by the local governor described the youths as members of a "terrorist organisation," adding that one police officer died in the incident.

The pro-Kurdish Firat News Agency (ANF) said the youths in the house had been dressed in "civilian clothes" and all but one had been shot in the head.

A local deputy from the pro-Kurdish People's Democracy Party (HDP) described the incident as a "mass execution".

"They are all young people in civilian clothes, as has been conveyed to us by those who saw the bodies," Tugba Hezer told ANF. "Not every single one of them can possibly be shot in the head during a clash. It is not possible.

"This is a mass execution."

He said that police were blockading the scene of the incident and the local hospital where the bodies had been taken.

Video footage released by the Dogan News Agency appeared to show the aftermath of the raid in the city, with bodies lying in the snow:

#Turkey: Video shows after Kurdish civilians killed by criminal Turkish regime forces in the city of #Van, Kurdistan pic.twitter.com/o7uOs1EFSB — curdistani (@curdistani) January 10, 2016

The raid marks one of the bloodiest weekends in Turkey's southeast since the collapse of a two-year ceasefire between the Turkish state and the Kurdistan Workers Party (PKK) in July 2015.

On Saturday, 16 suspected Kurdish militants were killed in the towns of Silopi and Cizre, while another four were killed in the Sur district in the city of Diyarbakir.

Human Rights Watch has criticised the Turkish security forces' operations in the southeast of the country, describing their actions as "disproportionate".

“The Turkish government should rein in its security forces, immediately stop the abusive and disproportionate use of force, and investigate the deaths and injuries caused by its operations,” said Emma Sinclair-Webb, senior Turkey researcher at Human Rights Watch.

“To ignore or cover up what’s happening to the region’s Kurdish population would only confirm the widely held belief in the southeast that when it comes to police and military operations against Kurdish armed groups, there are no limits – there is no law.”

The Turkish government claims that since July more than 3,100 militants have been killed in Turkey and in air strikes on the PKK headquarters in northern Iraq.

The PKK heavily disputes this figure, saying that around 220 guerrilla fighters have been killed, along with over 100 civilians.

More than 200 members of the Turkish security services have been killed by Kurdish and left-wing militants, according to the government.

Since the beginning of the PKK's guerilla war against the Turkish state in 1984, more than 40,000 people have been killed, with human rights abuses reported on both sides.