Russian forces launched a heavy bombardment against insurgent-held areas in Syria's Latakia province on Wednesday, near where a Russian warplane had been shot down by Turkey the day before, rebels and a monitoring group said.
At least 12 air strikes hit Latakia's northern countryside as pro-government forces clashed with fighters from al Qaeda's Nusra Front and Turkmen insurgents in the Jabal Akrad and Jabal Turkman areas, the British-based Syrian Observatory for Human Rights said.
A Turkmen commander said missiles fired from Russian warships in the Mediterranean were also hitting the area, as well as heavy artillery shelling.
Hassan Haj Ali, the head of Liwa Suqour al-Jabal, a rebel group operating in western Syria, also said there were fierce battles in the area, with Russian aircraft supporting pro-government forces.
Turkey on Tuesday shot down a Russian warplane that it said had entered Turkish airspace, something denied by Moscow.
It crashed in the Jabal Turkman area, the Observatory said.
Both pilots bailed out. The Russian Defence Ministry said one had been shot dead from the ground as he parachuted down, but that one was safe and had returned to Russia's air base in western Syria.
However, a deputy commander of rebel Turkmen forces in Syria said on Tuesday that his men had shot both pilots dead as they parachuted down.
The incident was one of the most serious publicly acknowledged clashes for half a century between Russia and a NATO member country.
A Turkish military source said Turkish troops on the border were on alert on Wednesday after the bombardment began.
Russia began intervening in the Syrian civil war on Sept. 30 in support of President Bashar al-Assad, whose forces are fighting insurgents backed by regional powers including Turkey.
The Russian air raids, launched ostensibly to target Islamic State, have mostly hit other, foreign-backed rebel groups, the United States says.
There have been strikes for several weeks in Latakia province, whose capital of the same name is Assad's coastal stronghold, but the Observatory said Wednesday's bombardments were particularly heavy.