Opposition commanders are saying Russia has taken a further step to back the offensive in northwestern Syria's Idlib by the Bashar Assad regime, which has been struggling to make gains in the province.

It was first time Russian officers were directly involved in clashes in the front, Reuters reported according to senior commanders. The Russian ground forces were involved in the fighting with the regime on the Humaymat hilltops in northern Hama that fell into opposition hands last week. With the Russian army's involvement, the hilltops were regained from the opposition forces after aborted successive attempts by the regime.

"These special Russian forces are now present on the battlefield. The Russians are intervening directly now," said Capt. Naji Mustafa, spokesman for the Turkey-backed National Liberation Front (NLF) coalition of opposition factions.

"When Assad's forces failed to advance, Russia then intervened directly... after bombing the area with more than 200 sorties," he added.

Meanwhile, the Russian military yesterday denied claims by Syrian opposition groups that there are active Russian ground forces in the war-torn country. "There have been no Russian ground forces in Syria, and there are none at present," the Russian Defense Ministry said in a statement carried by state news agency TASS. The Assad regime intensified its attacks starting April 26 under the pretext of fighting Hayat Tahrir al-Sham (HTS) militants holed up in Idlib, despite the de-escalation agreement.

The Assad regime's intermittent attacks and bombardment have killed, wounded and displaced thousands of people in Idlib. Civilian areas have been destroyed by indiscriminate attacks, while numerous educational facilities, health facilities and residential areas have collapsed or have become unusable after being targeted by bombs. Despite the fact that almost three months have passed since Assad regime launched the offensive, it has suffered from grave losses and made no gains on the ground, except some areas that often change hands.

The head of a major opposition group said Moscow's deployment of undisclosed numbers of ground forces came only after elite regime troops known as the Tiger Forces and allied militias were unable to make "any significant territorial gains."

"The Syrian army found itself in a crisis and were forced to ask for Russian troops on the battlefield," said Jamil al-Saleh, the head of the Jaish al-Izza opposition group.

Being the last opposition enclave, Idlib's prewar population of 1.5 million has swelled to around 3 million with new refugee waves after it was designated a de-escalation zone under the Astana agreement between Turkey, Russia and Iran in May 2017 to pave the way for a permanent political solution in Syria. Tens of thousands of Syrians trapped in other parts of the country were evacuated there under various cease-fire agreements.