The Israeli government is to retroactively legalise four unauthorised settler outposts in the West Bank in a move likely to exasperate the US secretary of state, John Kerry, before his fourth visit to Jerusalem next week in a drive to restart peace talks.

The measure comes amid a heightened spate of attacks on Palestinians and their property after the killing of a settler in the West Bank last month. The so-called price tag attacks prompted an emergency meeting of government ministers and security officials on Thursday to discuss tougher measures in dealing with settler extremism.

The government said it had taken steps to confer legal status on the four outposts, which have been slated for demolition since 2003, in response to a petition submitted to the supreme court by the Israeli settlement monitoring organisation Peace Now.

Officials draw a distinction between about 120 West Bank settlements whose construction was approved by the government, and dozens of small unauthorised hilltop outposts, invariably populated by young, hardline ideologically and religiously driven settlers. Under international law, all settlements in the West Bank and East Jerusalem are illegal.

The legalisation move is likely to increase already widespread pessimism over the chances of success for Kerry's mission to revive the peace process. Settlement expansion is a key deterrent to the Palestinians returning to the negotiating table.

Yariv Oppenheimer, the director of Peace Now, said: "Instead of defending Israel's interest, the defence minister is defending the security of the hilltop youth. This is a slap in the face to the efforts of the US secretary of state to restart negotiations."

The Palestinian official Hanan Ashrawi said the move showed "the truth of an ongoing Israeli policy to create facts on the ground. It pre-empts Kerry's visit to the region next week, and makes a mockery at any attempt to launch viable negotiations. These actions send a clear message to both the Obama administration and to the Palestinian people that Israel is committed more to land theft than to peacemaking."

Last week preliminary approval was given to the construction of 300 housing units at the settlement of Beit El, close to the Palestinian city of Ramallah. The announcement was made despite reports that the Israeli prime minister, Binyamin Netanyahu, had agreed to an unannounced short-term de facto moratorium on settlement construction while Kerry pursued his peace mission.

Meanwhile, attacks by settlers on Palestinians and their property have risen since the murder of Eviator Borovzky, 30, in the West Bank just over a fortnight ago.

This week, Muslim graves in the village of Sawiya have been vandalised, wheat fields near the village of Beit Furik have been torched, and 1,200 olive saplings near Akraba have been uprooted, according to Ghassan Daghlas, a Palestinian official who monitors settler attacks.

The latest development was the targeting of Palestinian schools, he said. An attempt to set fire to a school in Ein Yabous village was thwarted this week by security guards, and settlers had thrown stones at school buses. "People are really upset and frightened," he said.

Graffiti was sprayed on the walls of a mosque and several cars were torched in Umm al-Qutuf, an Arab village in Israel near the Green Line, Israel Radio reported. The public security minister, Yitzhak Aharonovich, viewed the attacks with gravity and said police were hunting for those responsible.

A statement from the justice ministry issued on Thursday evening confirmed that a high-level meeting to discuss settler violence had discussed "the need for more serious steps to be taken, including making sure law enforcement have the tools at hand to deal with the criminals responsible".

A measure is to be brought before the cabinet next week following the meeting between Shin Bet officials, the Israeli Defence Forces and government ministers, including Aharonovich, justice minister Tzipi Livni and the attorney general, Yehuda Weinstein.

Security sources told the Guardian that since the beginning of 2012, 33 administrative orders had been issued against rightwing extremists, ordering them to leave the West Bank for varying periods. The orders, signed at the request of the Shin Bet, Israel's internal security agency, were issued to Israelis considered a potential risk to the security and stability of the region, the sources said.

About half a million settlers live in the West Bank and East Jerusalem, of whom a tiny minority engage in violent attacks on Palestinians.

• This article was amended on Friday 17 May 2013 to include details of the justice ministry statement on Thursday 16 May.