The Russian airplane crash site on the Sinai Peninsula is pictured in this handout photo satellite image provided by Russian Emergencies Ministry on November 1, 2015.  [Photo/Agencies]

"This is a complicated matter and requires advanced technologies and broad investigations that could take months," Sisi said in a televised speech on Sunday.

The wreckage was found in a desolate area of stony ground.

Rescuers had collected the colourful suitcases of the passengers into a pile. A pink child's sandal decorated with white flowers lay among the debris, a reminder that 17 children were among those killed as they headed home from their holidays.

Parts of the wreckage were blackened and charred, with one section forming heaps of twisted metal, although the blue Metrojet logo was still visible on its broken tail fin.

As the Russian investigators moved slowly across the site, Egyptian military helicopters buzzed overhead, combing the wider area for debris - or bodies - not yet found.

MORGUE

At least 163 bodies had already been recovered and transported to various hospitals including Zeinhom morgue in Cairo, according to a cabinet statement.

Airport security sources said Russian experts who arrived on Saturday brought with them refrigerators and DNA samples to help identify and take home the dead.

Russian experts had already visited the morgue on Saturday night and Moscow's ambassador to Cairo said the first 130 bodies were due to leave on Sunday evening bound for St Petersburg.

A source inside the morgue said the bodies had been numbered using bracelets, ready to be received by the Russians, and empty ambulances were arriving to pick them up.

Those on board the doomed flight included 214 Russians, at least three Ukrainians and one Belarusian, most returning from the Red Sea, popular with Russians seeking winter sun.

The Russian flag was flying at half-mast over the country's embassy in Cairo on Sunday morning. President Vladimir Putin has declared a day of national mourning in Russia.

Russia's transport regulator said in a statement that it had grounded Kogalymavia's Airbus A321s until the reasons for the crash became clear.

Russian transport prosecutors have already examined the quality of the fuel used by the airliner and found that it met necessary requirements, Russia's state-run RIA news agency said.

The crew had also undergone medical tests recently and no problems were detected, Interfax reported.

Experts from Airbus have begun arriving in Egypt to assist in the investigation, the civil aviation ministry said.

Emergency services and aviation specialists resumed early on Sunday their search at the crash site which is spread over more than 15 square km, with 100 Russian emergency workers helping them recover bodies and gather evidence.

Russia, an ally of Syrian President Bashar al-Assad, launched air raids against opposition groups in Syria including Islamic State on Sept. 30.

Islamic State, the ultra-hardline group that controls large parts of Iraq and Syria, has called for a holy war against both Russia and the United States in response to airstrikes on its fighters in Syria.

Sinai is the scene of an insurgency by militants close to Islamic State, who have killed hundreds of Egyptian soldiers and police and have also attacked Western targets in recent months. Much of the Sinai is a restricted military zone.

Militants in the area are not believed to have missiles capable of hitting a plane at 30,000 feet.