Russian air strikes killed at least 13 people in rebel-held northwest Syria on Sunday, the deadliest attack on the country this year, a war monitor said.

At least nine civilians, including two children, were among the dead, with most killed at a fruit and vegetable market in Jisr al-Shugur in the Idlib region.

"These Russian strikes are the deadliest in Syria this year and amount to a massacre," said Rami Abdel Rahman, who heads the Britain-based Syrian Observatory for Human Rights.

Russian air strikes Sunday on Syria's northwest killed at least 11 people including seven civilians, in retaliation for deadly drone attacks blamed on rebel forces, a war monitor said.

"Six civilians were killed in Jisr al-Shughur and three rebel fighters were killed nearby by Russian air strikes," Rami Abdel Rahman, who heads the Syrian Observatory for Human Rights, told AFP.

Ahmed Yezidi of the civil defence in Jisr al-Shughur, a city in rebel-held Idlib province, said the strikes killed nine people, without specifying whether fighters were included in the toll.

Braving the scorching Saudi heat, Mecca resident Amer Abdullah distributed free tea and bread to worshippers performing the annual hajj pilgrimage, honouring a long-standing tradition in Islam's holiest city.

Joined by his five sons, the 45-year-old Saudi man who spends his evenings serving warm beverages to worn-out Muslim pilgrims, said hajj hospitality runs in his blood.

"For the people of Mecca, there is no higher honour than serving pilgrims," Abdullah told AFP ahead of the start of hajj rituals on Sunday.

Vast crowds of robed Muslim faithful walked solemn circles around the Kaaba, the black cube at Mecca's Grand Mosque on Sunday to begin the biggest hajj pilgrimage in several years, in the heat of the Saudi summer.

Islam's holiest site is expected to host more than two million worshippers from 160 countries during the annual rites that could break attendance records, with 1.6 million foreigners already arrived by late Friday.

Israelis kept up their months-old protests against the government's judicial overhaul Saturday, days after Prime Minister Benjamin Netanyahu vowed to press on with the controversial programme.

Brandishing banners reading "Israel is burning" and deeming Netanyahu an "enemy of democracy", demonstrators thronged the heart of the commercial hub of Tel Aviv.

While there was no immediate turnout figure, the weekly rallies have regularly drawn tens of thousands.

Artillery fire, air strikes and gun battles rocked Sudan's capital on Saturday, witnesses told AFP, as the UN urged a stop to "wanton killings" that have left decomposing bodies in Darfur.

While fighting rages, relief efforts have stalled after more than two months of fighting between rival generals.

Houses in Khartoum shook from the fighting that continued unabated, residents said, with entire families sheltering in place, running low on vital supplies in the baking summer heat.

The hajj pilgrimage has given Sudanese faithful Kamal Kabashi a brief respite from his country's bloody conflict. Having safely arrived in Islam's holiest city, he was praying for peace.

Only weeks ago his home in North Darfur state, in Sudan's west, was hit by shelling as a power struggle between rival generals spiralled into an all-out war.

Kabashi, his wife and their five children were unharmed as they had relocated to a safer neighbourhood of El Fasher, the state capital, days before.

Desperately needed relief supplies are being confiscated by the warring parties in Sudan as fighting spreads to areas previously untouched by the 10-week-old conflict between top generals, aid agencies said on Friday.

Demonstrations in support of the regular army were held Friday in greater Khartoum and in White Nile state to its south as civilians gave vent to their anger at the widespread requisition of private homes by the rival paramilitaries of the Rapid Support Forces (RSF), witnesses said.

The Israeli army acknowledged Friday it "failed" to prevent an attack by Jewish settlers on a Palestinian village in the occupied West Bank, during which one villager was killed.

Revenge attacks on Turmus Ayya and other villages followed the killing of four Israelis by Palestinian gunmen on Tuesday, which militant group Hamas said was in response to an Israeli army raid on Jenin refugee camp which killed six Palestinians the previous day.

Army spokesman Daniel Hagari said troops had tried to prevent Israelis from attacking Turmus Ayya but they were stretched too thin.

United Nations aid transited Friday from regime-controlled northwest Syria to rebel-held areas for the first time since a devastating February earthquake, an AFP correspondent and a humanitarian official said.

The correspondent saw the 10-truck convoy reach rebel-held Al-Nayrab in Idlib province from the direction of regime-held Saraqib, headed for storage facilities near the Turkish border.

The last such convoy was in January, according to a humanitarian official in Idlib who requested anonymity as they were not authorised to speak to the media.