Moscow (AFP) - One of two pilots aboard a Russian warplane shot down by Turkey on Tuesday was killed by fire from the ground after he ejected from the craft, the Russian military said, citing preliminary information.

Military spokesman General Sergei Rudskoi said a Russian soldier had also been killed in a failed bid to rescue the pilots, whose Su-24 plane crashed in Syrian territory.

Rudskoi said Russia would cease all military contact with Turkey, as international concerns grow that the incident could snowball into a major conflict.

The general said the Su-24 "fell in Syrian territory, four kilometres (2.5 miles) from the border".

"The crew ejected," the general said. "According to preliminary information, one of the pilots died after being fired upon from the ground."

The fate of the second pilot was not immediately known.

In a statement published on the defence ministry's website, Rudskoi said a Russian soldier had been killed when his Mi-8 helicopter was "damaged by gunfire and had to land" during a search-and-rescue operation to retrieve the pair.

Two helicopters were used in the operation.

The rest of the crew onboard the stricken Mi-8 were evacuated to the Hmeimim air base in Syria's northern Latakia province, Rudskoi said, adding that the helicopter was hit by mortar fire coming from territory under rebel control.

The Turkish army said earlier the fighter was shot down by two of its F-16s after it violated Turkish airspace 10 times within a five-minute period.

Rudskoi insisted the Su-24 had not strayed within Turkish airspace, and denied that the Turkish army had tried to make either radio or visual contact with its pilots before shooting it down.

He said the plane was shot down within Syrian airspace and condemned it as a "flagrant violation of international law" that would have "the gravest consequences".

He said that Russia's Moskva guided missile cruiser would be stationed near Latakia.

"All targets representing a potential threat to us will be destroyed," he warned.

Russian bombers, which launched strikes on Syria in defence of President Bashar al-Assad on September 30, will now be escorted by fighters, Rudskoi announced, adding that operations to retrieve the two pilots were continuing.