At least 38 Islamic State fighters were killed over the last 24 hours as Syrian jets continued to pound the extremist group’s strongholds in the ancient city of Palmyra, the Syrian Observatory for Human Rights said on Tuesday.
A Syrian military source, who declined to be named, said that newly supplied Russian aircraft flown by Syrian pilots had been used in the attacks.
Russia has reportedly stepped up its military assistance to the embattled regime of Syrian President Bashar Assad, which is under growing pressure from Islamic State and from mainly Islamist Turkish- and Gulf-backed rebels.
The US Defence Department said last week that it was monitoring a Russian military buildup at an airport near the port city of Latakia in Assad’s coastal heartland.
US Defence Secretary Ash Carter on Friday discussed the situation in Syria in a telephone call with his Russian counterpart.
Russia has acknowledged that it is sending military equipment to Syria, saying that it is intended to fight terrorism.
The new aircraft arrived in Syria about 10 days ago and were first deployed last week in air raids on Islamic State’s de facto Syrian capital, the northeastern city of al-Raqqa, the source said.
He added that government forces have also used newly supplied ground artillery against rebels in mountains northeast of Latakia.
The Syrian air force has intensified its raids on Palmyra in Syria’s central desert in recent days.
Rami Abdel-Rahman, head of the opposition Britain-based Observatory, described a barrage last week as “one of the strongest attacks” by Syrian warplanes since the Islamic State group captured the city in May.
Abdel-Rahman said his sources confirmed that newly supplied Russian aircraft had been used in the raids on Palmyra.
Most Palmyra residents have fled the city. Only a few of the original inhabitants and the families of militants still live there.
The jihadist group have blown up the 2 000-year-old Temple of Bel and some of the famed tower tombs in Palmyra since capturing the Unesco-listed World Heritage Site in May.