The sound of machinegun fire and explosions were heard from Russia's main base in Syria on Tuesday, residents of the area said, but it was not immediately clear whether the base had come under attack.
Residents told The National they had spotted drones around the Hmeimim airbase, and that explosions had been heard in the area.
"We have been hearing the sound of drones, explosions, and machinegun fire since the morning,” said a resident who lives 2km from the base. Another resident said Russia had jammed mobile phone communications in the area.
The Syrian Observatory for Human Rights, a UK-based monitor that relies on a network of sources in Syria, said that Syrian government auxiliaries are likely to have carried out an attack on the base.
However, another resident said Russian troops were conducting exercises with drones, mortar rounds and other weapons inside the base. He said Syrian government troops, accompanied by auxiliaries, had moved closer to the base in response but disputed reports that the two sides clashed.
"This is not the first time that this happened," he said, saying a similar scenario had unfolded earlier this month. There was no comment from Moscow or Damascus.
Hmeimim and another base in Syria's port city of Tartous are Russia's major warm-water outposts. Both are in the heartland of the Alawite sect of former dictator Bashar Al Assad, Russia's main Middle East ally until he was toppled in December.
Alawite allies of Russia dominated Syria for six decades until the Assad regime fell. In March, more than 1,300 Alawite civilians were killed in incursions by security forces and pro-government auxiliaries, which were met by ambushes and other forms of resistance.
On Tuesday, Russia's Tass news agency quoted Foreign Minister Sergey Lavrov as saying Moscow was concerned that: "Radical militant groups are carrying out real ethnic cleansing, mass killings of people based on their nationality and religion."
The Assad regime fell to an offensive led by Hayat Tahrir Al Sham (HTS), a militant group that was once allied with Al Qaeda. However, President Ahmad Al Shara, the HTS leader who took power in Damascus in January, has refrained from publicly criticising Moscow.
Russia's military intervention in Syria's civil war saved Mr Al Assad from defeat in 2015. By the time HTS-led forces swept through northern Syria towards Damascus in December, a similar rescue had become impossible, or too costly.
