David Cameron has urged his Turkish counterpart to ensure that Ankara maintains direct communications with Moscow to avoid an escalation in tensions after Turkish fighter jets shot down a Russian warplane.
Ahmet Davutoglu phoned Mr Cameron and explained that Turkey had taken protective action after the Russian jet was warned "several times" not to violate Turkish air space, said Downing Street.
Nato said its "stands in solidarity" with Turkey and called for "calm and de-escalation" after holding an emergency session in response to the incident.
Asked if the jet had been shot down over Turkey, Nato secretary general Jens Stoltenberg said: "The allied assessments we have got from several allies during the day are consistent with the information we have been provided with from Turkey."
Russian President Vladimir Putin warned of "significant consequences for Russian-Turkish relations".
It is thought to be the first time a plane from a member state of the transatlantic alliance has shot down a Russian aircraft in half a century.
Mr Cameron's official spokeswoman told a Westminster media briefing that in the 10-minute call, Mr Davutoglu "explained what had happened - that they had a Russian jet flying there, they had warned it several times not to violate Turkish air space, but it had then proceeded to do so and consequently they had taken action to protect their air space".
The spokeswoman added: "The Prime Minister strongly encouraged Prime Minister Davutoglu to make sure there was direct communication between the Turks and Russians on this, so a clearer understanding could be formed of what had happened and how to avoid this happening in the future and to avoid an escalation."
She played down suggestions that the incident might have an impact on Mr Cameron's effort to secure parliamentary approval to commit RAF planes to bombing missions against the Islamic State terror group - also known as Isil or Isis - in Syria. The PM is due to set out the case for extending UK air strikes in a statement to Parliament on Thursday, with a vote widely expected to follow on Tuesday.
"It doesn't change two important factors, which are the threat posed by Isil to the UK and the need to work in a coalition to be doing more - and the Prime Minister has said he believes in doing more - in Syria," said Mr Cameron's spokeswoman.
She added: "We are open to considering doing more with the Turks to look at how we work together to tackle Isil and protect ourselves from the threat of Isil."
The spokeswoman pointed out that RAF planes regularly pass through Turkish air space with permission on their way from their base at Akrotiri in Cyprus to carry out air strikes on IS militants in Iraq.
A number of coalition partners had already raised concerns with Russia over the need for its forces to maintain communication channels since Mr Putin launched air strikes in Syria in September, she said.
Moscow at first claimed the Su-24 jet was shot down by rebels opposed to Syrian president Bashad Assad, but later confirmed it was targeted by a Turkish F-16.
Mr Putin said: "It fell on Syrian territory, four kilometres from the Turkish border. When it was attacked in the air, it was flying at an altitude of 6,000 metres, one kilometre away from the Turkish territory. In any case, our plane and our pilots were in no way a threat to the Turkish Republic in any way. This is obvious."
Russian foreign minister Sergey Lavrov cancelled a visit to Turkey planned for Wednesday.
Mr Davutoglu insisted his country has the right to take "all kinds of measures" against violations of its air space, and called on the international community to work towards "extinguishing the fire that is burning in Syria".
Video footage of the incident showed a plane on fire before crashing on a hill and two crew members apparently ejecting.
Jahed Ahmad, of the 10th Brigade in the Coast, said the crew members tried to land with their parachutes in Syrian government-held areas after they ejected, but came under fire from members of his group.
He added that rebels shot one of the pilots, who landed dead on the ground. The fate of the second pilot was not immediately known.