Britain has told Russia and Egypt that the country is ready to deploy its special forces unit to "kill or capture" Abu Osama al-Masri, an Egyptian cleric and the frontman of an Isis-offshoot group, alleged to be the mastermind behind the  Russian plane bombing plot.

Britain extended its support to both Russia and Egypt after reports confirmed that the Metrojet plane, carrying mostly Russian tourists from the Egyptian resort of Sharm el-Sheikh to the western Russian city of St Petersburg, was brought down by a bomb planted on board the aircraft by an Isis-affiliate group headed by Abu Osama al-Masri.

Al-Masri recently had appeared in an Isis video and taken responsibility for bringing down the plane.

Al-Masri, 42, is a former scholar of the al-Azhar university in Cairo, a 1,000-year-old Sunni Muslim institution. In November 2014,  his Sinai-based organisation pledged allegiance to Isis.

The British intelligence officials  are also investigating the shadowy chief of this Isis' offshoot in Egypt for his role in planting the bomb in the hold of the Russian passenger plane, according to The Sunday Times.

It is not clear yet whether either Russia or Egypt has accepted Britain's offer to deploy its special forces to hunt down the Isis cleric.

In recent days, the United States has also expressed confidence that it was a bomb planted by a  Islamic terrorist, which brought down the Russian passenger plane over Egypt.

Several top US officials from intelligence, military and national security told CNN there was a strong possibility that a bomb on Metrojet Flight 9268 led to the crash.