The United Nations rights office said Tuesday it was "deeply concerned" by the escalation of violence in the occupied Palestinian territories, east Jerusalem and Israel.

The Office of the UN High Commissioner for Human Rights appealed for calm after several days of unrest.

Tensions in Jerusalem have flared into the city's worst disturbances since 2017 after Israeli riot police clashed with large crowds of Palestinian worshippers on the last Friday of the Muslim holy fasting month of Ramadan.

Israel and Hamas exchanged heavy fire on Tuesday, with at least 25 Palestinians killed in Gaza.

"We are deeply concerned at the escalation of violence in the occupied Palestinian territory, including east Jerusalem, and Israel in the past days," Rupert Colville, spokesman for UN rights chief Michelle Bachelet's office, told reporters in Geneva.

"We condemn all violence and all incitement to violence and ethnic division and provocations." 

He urged Israeli security forces to allow "the right to freedoms of expression, association and assembly".

"No force should be used against those exercising their rights peacefully."

More than 200 rockets have been fired by Palestinian militants from the Gaza Strip towards Israel since Monday.

"The use of indiscriminate weapons, such as the rockets being fired into Israel, is strictly prohibited under international humanitarian law and must stop immediately," said Colville.

Israel has responded with 130 strikes carried out by fighter jets and attack helicopters on military targets in the Gaza enclave.

"Israel must respect international humanitarian law," said Colville, adding that any attacks should be directed at military objectives, with precautions taken to avoid civilian deaths.

Meanwhile the UN special rapporteurs on human rights in the Palestinian territories and on adequate housing, Michael Lynk and Balakrishnan Rajagopal, condemned the Israeli security forces' response to the protests.

"The immediate source of the current tensions in east Jerusalem are the actions of Israeli settler organisations, whose stated aim is to turn Palestinian neighbourhoods into Jewish neighbourhoods," they said.

"Neither short-term calm nor long-term peace will be accomplished as long as the national and individual rights of the city's Palestinian population are routinely abrogated."

Special rapporteurs do not speak for the UN but report their findings to it.