In this Sept. 15, 2015 photo shows, satellite image with annotations provided by GeoNorth, AllSource Analysis, Airbus shows Russian tanks and armed personnel carriers at an air base in Latakia province, Syria.

Syria said Tuesday it had received sophisticated new arms from Russia including warplanes and deployed them against militants, as signs grew of a major shift in the country’s four-year conflict.

A senior Syrian military official told AFP Damascus had received a fresh batch of arms, including at least five fighter planes, while a monitoring group said there had been a marked increase in regime attacks on Daesh.

The deliveries came amid a rapid Russian military build-up in Syria, with US officials saying Moscow had deployed 28 combat planes and begun drone flights in the country.

The Syrian military official told AFP the new warplanes had arrived on Friday along with reconnaissance aircraft at a military base in Latakia province, the traditional heartland of President Bashar Assad’s regime.

The regime had also received “sophisticated military equipment to fight IS” including targeting equipment and precision-guided missiles, the official said, speaking on condition of anonymity.

The new weapons had already been deployed against Daesh in the cities of Deir Ezzor and Raqqa, the militant group’s de facto capital in Syria.

“Russian weapons are starting to have an effect in Syria,” the official said.

Another military source in Latakia confirmed to AFP that the army had received spy planes and other equipment “that will allow Syrian ground and air forces to accurately identify targets.”

The Syrian Observatory for Human Rights, a monitoring group, said new Russian equipment was being put into action, with at least 38 Daesh fighters killed in air strikes in terrorist-held towns in central Syria on Monday.

“The number of raids is growing and the strikes are more precise after the Syrian air force received arms and more efficient planes from Moscow,” Observatory director Rami Abdel Rahman said.

On Monday, US officials said Moscow had deployed 28 fighter and bomber aircraft at the airfield, including 12 SU-24 attack aircraft, 12 SU-25 ground attack aircraft and four Flanker fighter jets.

The officials said there were also about 20 Russian combat and transport helicopters at the base and that Moscow was operating drone flights, but did not give additional details.

“They are not going to sit around and defend the airfield or maybe even the province of Latakia,” said Jeffrey White of the Washington Institute for Near East Policy.

“This kind of aircraft suggests that the Russians intend to exert their combat power outside of Latakia in an offensive role.”

The deployments have raised fears of an inadvertent confrontation between Russian forces and the US-led coalition that has been carrying out almost daily air strikes against IS in Syria for more than a year.