Syria regime and rebels battle in Hama province
Fighting between Syrian regime forces and rebel factions continued on Thursday as a government offensive on opposition-held Hama and Idlib continued for a second day on Thursday.
Syria's General Ali Ayoub announced a "wide-ranging" government offensive in Hama and Idlib provinces - north-western Syria - to roll back rebel advances who have been inching closer to the regime's stronghold in Latakia.
Ayoub said that Russia has proviced air cover for its troops in Hama province.
US Defence Secretary Ashton Carterwarned that Russia can expect to suffer casualties in Syria in the coming days.
"[Russian military support] will have consequences for Russia itself which is rightly fearful of attack... in the coming days, the Russians will begin to suffer casualties," Carter said at a NATO meeting in Brussles.
Russia surprised the US and its NATO allies when it launched air raids inside Syria last week, after expanding its military presence in Syria's coastal regions.
Russia's defence secretary said its air force launched 27 air raids in Homs, Hama and Raqqa, on Thursday.
Opposition activists say that rebel forces have so far stalled the regime advance.
At least one aircraft - claimed to be Russian - was downed in Kafr Nadouba in Hama's northern countryside, the Syrian Observatory of Human Rights said.
Activists said that another helicopter also crashed close to the frontlines.
Russia has between four and six Mi-24 Hind attack helicopters stationed at Latakia'a Basel al-Assad airbase, according Ruslan Leviev, a Russian investigative journalist.
There were no reports about the whereabouts of the crew.
The Syrian airforce also operates the export version of the aircraft.
Syrian and Russian jets have violated Turkish airspace a number of times this week with NATO warning Moscow that it was ready to defend the member state.
There were further unconfirmed reports on Thuerday that a Russian war plane was shot down over Turkey after violating its airspace.
Meanwhile, air strikes took place in Sahl al-Ghab, Hama and Homs were fighting has been taking place. Jobar in Damascus' suburbs also witnessed heavy fighting.
Rebel coalition Ahrar al-Sham - based in northern Syria - said they had destroyed 18 tanks, four armoured personnel carriers, and five machine gun-mounted vehicles in northern Hama.
The group also claimed to have killed 50 goverment troops and injured a further 100 more in the north-west provice.