PRAGUE: Russia's entry into the war in Syria has changed the balance on the ground, Syrian President Bashar al-Assad said in an interview on Czech Television, and he predicted that support from his main international ally would remain strong.

In the interview, conducted in Damascus on Sunday and aired on Tuesday, Assad said the downing of a Russian warplane by regional foe Turkey on Nov. 24 showed Ankara's dissatisfaction with developments on the ground in Syria, which he said had been moving in the government's favour.

"I think it (the plane incident) has shown the real intention of (Turkish President Tayyip) Erdogan, how he lost his nerve just because the Russian intervention has changed the balance on the ground," Assad said.

"The war against terrorism is continuing. The Russian support or participation is going to be stronger. It is stronger anyway. There is no way back in that regard," he said.

Turkey, which says Assad's departure must be part of any long-term solution in Syria, has said the Russian jet violated Turkish airspace - something that Russia denies.

Russia, the main international supporter of Assad, has been bombing insurgent positions in western Syria near where its warplane crashed, including areas held by Turkmen rebels supported by Ankara.

Assad said militant groups would get full amnesty if they are ready to lay down arms but added that this was not an option that jihadist groups like Islamic State or al Qaeda's Syria wing Nusra Front were likely to take.

"When they give up their arms, and go back to their normal life, the government (will) offer them amnesty," he said.

"You are not charged with any (crime), you are free to go to your normal life, but go back to your normal life, peaceful life," he said.

Syrian government officials said on Tuesday they had agreed on a deal for opposition "gunmen" to leave the last insurgent-held area of the city of Homs.

It was the latest example of a local ceasefire agreement being reached in Syria in the absence of a national solution to the nearly five-year conflict which has killed some 250,000 people.

Assad said the government had not ruled out dealing with "terrorists" - a term used by Damascus to describe all insurgents fighting in Syria.

"If they want to change their position of course we have to deal with them," he said.

"But when you talk about ISIS (Islamic State) and al Nusra and al Qaeda offshoots, they are not ready to give up their arms, they are not ready to make negotiations with the government anyway," he said.

Assad also said in the interview that terrorists were mixed among Syrian refugees to Europe.