Turkey and US say Russian jets could be shot down

US secretary of state John Kerry said, while visiting Chile: "It's precisely the kind of thing that, had Turkey responded under its rights, could have resulted in a shoot-down".

"We've engaged in initial conversations with Russia about making certain that there is no possibility of accidental conflict".

Mark Toner, a State Department spokesman, added, in Washington: "We view this [Russian] incursion as reckless, and it's dangerous, provocative".

The warnings come after Russian jets skirted over Turkish territory on two occasions on Saturday and Sunday.

Igor Konashenkov, a Russian defence official, told press on Monday that Saturday's incident involved a Sukhoi-30 bomber which crossed the Syrian-Turkish border "for a few seconds" due to "unfavourable weather conditions".

The Turkish and US warnings were echoed by Nato and EU structures.

Nato ambassadors, after holding an emergency meeting on Monday in Brussels, said: "The aircraft in question entered Turkish airspace despite Turkish authorities' clear, timely, and repeated warnings".

They spoke of "the extreme danger of such irresponsible behaviour".

Federica Mogherini, the EU's foreign policy chief, who met her Turkish counterpart in the EU capital the same day, spoke of "unacceptable violations" of Turkish airspace.

The complaints come amid broader US and EU criticism of Russian air strikes on Western-backed anti-government rebels in Syria.

US officials told the New York Times that Russia’s targets include rebel groups such as Tajamu al-Ezzeh and the First Coastal Division, which are being trained and equipped by the US intelligence agency, the CIA.

Zbigniew Brzezinski, a former national security advisor, wrote in an op-ed in the Financial Times that if Russia tries to destroy US "assets" the US should retaliate.

"The Russian naval and air presences in Syria are vulnerable, isolated geographically from their homeland … They could be 'disarmed' if they persist in provoking the US”, he noted.

"It is time … for strategic boldness".

But for his part, Vladimir Komoyedov, the head of the armed forces committee in the Russian parliament, indicated the Russian campaign could be widened to involve ground forces.

He said if Russian volunteer brigades active in east Ukraine want to fight jihadists in Syria, then they “cannot be stopped.”

The State Department’s Toner on Monday also said if Russia wants to join the US-led anti-Islamic State coalition "then we would see a role for them".

The offer of cooperation was echoed by the Finnish president, Sauli Niinisto, in an interview with the Reuters news agency.

"We're in a situation where both good and very bad outcomes are possible", he said,

"[But] if Russia and United States can find something common in Syria, that would reflect on [a solution in] Ukraine”, he added, amid EU-brokered efforts to freeze fighting in east Ukraine.