The Israeli military has tripled its demolitions of Palestinian-owned structures in the occupied territories over the past three months, a United Nations' report says.

Figures collated by the UN's office for the coordination of humanitarian affairs (OCHA) - which operates in Gaza, the West Bank and East Jerusalem - show from an average of 50 demolitions a month in 2012-2015, the number rose to 165 since January, with 235 demolitions in February alone.

On Thursday, Israeli authorities demolished Palestinian buildings in al-Khan al-Ahmar village near the West Bank city of Jericho, and in Khirbet Tana village near Nablus.

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One of the owners of the demolished structures in al-Khan al-Ahmar, Hussein Kaabneh, said the demolition team came in the morning without warning.

"I was surprised by the police and army … so I was very mad. I asked them, 'Why do you want to demolish it?' I did not get a warning or anything. And he told me, 'You are [your structure is] not legal'," Kaabneh told Reuters news agency.

The Israeli military, which has occupied the West Bank since the 1967 Middle East war, says it carries out the demolitions because the structures are illegal: either built without a permit, in a closed military area or firing zone, or violating other planning and zoning restrictions.

The UN and rights groups point out that permits are almost impossible for Palestinians to acquire, that firing zones are often declared but seldom used, and many planning restrictions date from the British Mandate in the 1930s.

The UN report on demolitions has alarmed diplomats and human rights groups over what they regard as a sustained violation of international law.

"It is a very marked and worrying increase," said Catherine Cook, an OCHA official based in Jerusalem who closely monitors the demolitions, describing the situation as the worst since the UN body started collecting figures in 2009.

"The hardest hit are Bedouin and Palestinian farming communities who are at risk of forcible transfer, which is a clear violation of international law," she said.

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The demolished structures include houses, Bedouin tents, livestock pens, outhouses and schools. In an increasing number of cases, it also includes humanitarian buildings erected by the European Union to help those affected by earlier demolitions.

Appearing before a sub-committee in the Israeli parliament on Wednesday, Major-General Yoav Mordechai - coordinator of the Israeli government's activities in the West Bank - defended the demolition policy and told politicians he was doing all he could to carry out 11,000 outstanding destruction orders.

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The politicians summoned Mordechai to the hearing because of concerns he is not doing enough to dismantle Palestinian structures, and focusing instead on removing unauthorised Israeli construction in the West Bank.

"I want to state unequivocally that enforcement is more severe towards the Palestinians," Mordechai told them.

"Moreover, much of the enforcement with regard to the Palestinians takes place on private Palestinian land."

According to B'Tselem, an Israeli human rights group, Mordechai's admission appears to confirm that Israel's policy discriminates against Palestinians.

"There is undoubtedly a wave of demolitions and displacements that is severely threatening the ability of thousands of Palestinians to live in these areas," said Sarit Michaeli, the spokeswoman for B'Tselem.

"To demolish the homes of Palestinians who are protected under the Geneva Conventions and to build [Israeli] settlements is a clear violation of international humanitarian law," she said.

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Last month, the European Union hit out at Israeli authorities after a school funded by the French government was demolished.

In the West Bank, an estimated 18 percent of the area has been declared by Israeli authorities as "firing zones", and 38 Palestinian communities are located within these areas.

Because the Israeli civil administration prohibits building in these areas, wide-scale demolitions frequently take place.

Throughout occupied West Bank and East Jerusalem, some 90,000 Palestinians are facing potential displacement, according to OCHA.