Russia has said one of its helicopters has crashed in Syria, killing the two pilots.

The Defence Ministry said the Mi-28N helicopter gunship crashed near Homs early on Tuesday after completing its mission. It said there is no evidence that it came under fire.

The ministry said the bodies of the pilots have been recovered and taken to the Hemeimeem air base on Syria's coast.

Russia has been carrying out air strikes since September 30 in support of Syrian government forces. The air campaign has allowed Russia to test some of its latest weapons, including the Mi-28 helicopter.

Meanwhile, a pro-government media outlet said Syrian troops have launched an offensive to retake a strategic hilltop village south of Aleppo from insurgents, including al Qaida's local affiliate.

Al-Manar TV said the attack on Tel al-Ais was launched on Tuesday. Al-Manar is run by Lebanon's Hezbollah militant group, which is fighting alongside Syrian government forces.

The village overlooks a supply line connecting the capital, Damascus, to the northern city of Aleppo, parts of which have been held by insurgents since 2012.

A coalition of insurgent factions captured Tel al-Ais earlier this month after heavy fighting despite a US and Russian-brokered ceasefire, which excludes the al Qaida-affiliated Nusra Front.

The Syrian Observatory for Human Rights, an activist-run monitoring group, said clashes are continuing around Tel al-Ais and the nearby village of Khan Touman.