US war planes strike IS weapons cache in Palmyra

US war planes have struck tanks and anti-aircraft weapons seized by Islamic State group fighters in Palmyra on Thursday, following the surprise capture of the Syrian city last weekend.

Among the weapons destroyed by US-led the anti-IS coalition were artillery, tanks and anti-aircraft systems, which the militants took from Russian and Syrian regime military bases in the Palmyra area.

"Coalition airstrike destroys a [IS] and artillery piece near Palmyra, Syria," the US-led Combined Joint Task Force said on its Facebook page, with a video showing the air strikes.

It comes after fears that heavy weaponry and possible anti-aircraft missiles seized by the militants could be used against Western targets or anti-IS forces.

Earlier this week, IS released a video showing militants inspecting a captured Russian military base with huge quantities of weapons left behind without being deactivated.

Russia and the Syrian regime have been criticised for concentrating its forces on capturing rebel-held areas of Aleppo, leaving Palmyra with few guards and easy prey for IS.

Russian war planes had also continued to bomb the densely populated rebel areas, with no air strikes on military bases or weapons' caches left to the militants.

This left the job up to US forces who destroyed 14 tanks and other heavy weaponry.

Washington also said it hinted it could send US forces to Palmyra to "clean up" the mess left by the Russians.

Meanwhile, pro-Syrian regime media has claimed that government forces were fighting back against IS in Palmyra.

Over a hundred 100 Hizballah fighters also arrived at the besieged T4 base near Palmyra on Wednesday, according to al-Masdar.

Syria's elite Tiger Forces unit led by notorious commander Suheil al-Hassan have also been sent to Palmyra from Aleppo, the pro-regime news site said.

Russian armed forces intervened in the Syria war in September 2015, launching air raids against rebel forces.

Moscow insists its air force only targets IS and al-Qaeda forces, but the vast majority of air strikes have been against opposition areas including homes, hospitals and schools.

Russia and the Syrian regime have been criticised for their lacklustre fight against IS, leaving the battle up to Kurdish and Syrian rebel fighters, backed by Turkish or US-led air forces.