Turkey's opposition parties have accused the government of responsibility for a massacre of 35 civilians killed near the village of Uludere in an air-strike. Pro-Kurdish Peace and Democracy Party (BDP) co-chair Selahattin Demirtas claimed that the killings were "clearly a massacre", according to Hurriyet daily news.

Prime Minister Recep Tayyip Erdogan's Justice and Development Party (AKP) admitted that the air strike, by F-16 fighter planes, was an "operational mistake". Demirtas repeated the same words Erdogan used to describe embattled Syrian leader Bashar al-Assad: "An administration that massacres its own people has no legitimacy."

Taraf newspaper harshly criticised the operation with a headline in the front page reading "The state bombed its people, 35 deaths".

Even the traditional anti-Kurdish Republican People's Party (CHP), the main opposition party, expressed concerns over the incident. CHP deputy chairman Sezgin Tanrikulu called for an investigation into the military operation and the punishment of those responsible.

According to reports, the civilians were petrol smugglers heading for the border with Iraq. Most of them lived in the village of Ortasu. Unmanned Aerial Vehicles (UAVs) mistook them as possible PKK militants crossing the border to attack Turkish targets.

"The incident took place within Turkish borders, in a place nearby the village," Uludere mayor Fehmi Yaman told Bianet news website. "These villagers were buying materials from Iraq and bringing them back to Turkey. When they were not allowed to enter the village, they turned back to Iraq. At this point the war planes attacked.

"Most corpses are heavily burned. Heavy machinery is needed to collect some bodies buried under rocks and debris."

A growing chorus of opposition to the government's policy of a military solution to the "Kurdish problem" is putting more pressure on Erdogan's government.

Nationalist newspaper Hurriyet' Murat Yetkin wrote: "The security dimension of the Kurdish problem is something you cannot avoid, but to rely on security measures in trying to solve a problem having political, ethnical, social and economic origin and depending on questionable methods could cost dearly."

The PKK is considered a terrorist organisation by Turkey, the EU and the US. The Turkish government's latest crackdown had already claimed 27 other lives in December.

More than 4,000 people, including dozens of journalists, have been arrested in 2011 under strict anti-terror laws. Mass trials of Kurds, including local politicians and human rights activists, have increased tensions between the government and the ethnic group.