Islamic State group jihadists killed 15 Syrian soldiers and allied fighters near Palmyra Friday, taking the government's losses in 24 hours of clashes to at least 49, a monitor said.

Hundreds of men may have gone missing after fleeing into government-controlled parts of Aleppo, the U.N. warned Friday, saying armed groups were reportedly blocking civilians from leaving the shrinking areas under their control.

A Saudi soldier was killed in a landmine blast near the kingdom's border with Yemen, the interior ministry said on Friday.

The bearded face of executed Shiite cleric Nimr al-Nimr is on every lamp post along the road leading towards his hometown of Awamiya, in Saudi Arabia's Eastern Province.

Russian Foreign Minister Sergei Lavrov said Friday that Syria's Aleppo will continue to come under bombardment as long as there are still rebels in the city.

"After a humanitarian pause, (the strikes) have resumed and will continue for as long as the bandits are still in Aleppo," Lavrov told journalists on the sidelines of the OSCE foreign ministers' meeting in Hamburg.

Syrian opposition groups are reportedly blocking civilians from fleeing the eastern part of Aleppo as regime troops advance in the city, the United Nations human rights office said Friday. 

The Islamic State group has threatened Egyptian followers of the mystical Sufi strand of Islam after claiming it beheaded two of their clerics in its Sinai Peninsula stronghold.

The group's affiliate in Egypt released pictures last month of a scimitar-wielding executioner beheading two elderly men it accused of "divination," a practice traditional Islam forbids.

A bombing killed six policemen at a checkpoint in Cairo on Friday, the latest in a series of attacks in the capital targeting security forces and officials, the interior ministry said.

The attack occurred in the western Talibiya neighbourhood of the capital, shortly before Muslim Friday prayers and when Cairo's streets are mostly empty.

Turkey is sending hundreds of commandos to reinforce its military campaign inside Syria, where the Turkish army has suffered increasing casualties in its fight to capture a key town from Islamic State jihadists, reports said on Friday.

A total of 300 commandos from a base in the western Turkish province of Denizli were first taken in buses to a military airport and then to the border region in military planes to join the Turkish-led operation, Turkish newspapers and the Anadolu news agency reported.

Syrian warplanes launched fresh raids on the last rebel-held districts in Aleppo on Friday, as key regime ally Russia vowed the assault would continue until opposition fighters left the battleground city.