Russia to track US planes as 'targets' as Syria tensions rise

Russia on Monday said it would track as "targets" any US-led coalition planes operating west of the Euphrates river in Syria, and condemned the shooting down of a Syrian government plane by US forces.

The US shot down a Syrian air force Su-22 over Tabqa - 55km west of Raqqa city - on Sunday, saying the plane was threatening allies from the Syrian Democratic Forces as they fought intense ground battles with Syrian government allies around Raqqa.

Any flying objects discovered west of the Euphrates river will be tracked as aerial targets by Russia's air defences

- Russian defence ministry

Russia's deputy defence minister, Sergei Ryabkov, said the incident was an "act of aggression". His ministry said the act voided a cooperation deal and that a military hotline for avoiding incidents in Syrian airspace had been suspended.

"The command of the coalition forces did not use the established communication channel for preventing incidents in Syrian airspace," the defence ministry said in a statement. 

As a result, it now "ends cooperation with the American side from 19 June based on a memorandum for prevention of incidents and ensuring safety of air flights during operations in Syria, and demands a careful investigation by the US command" of the downing.

"Any flying objects, including planes and drones of the international coalition, discovered west of the Euphrates river will be tracked as aerial targets by Russia's air defences on and above ground," it said.

The US military said later on Monday that it was repositioning its aircraft to ensure aircrew safety.

US defends downing of Syrian jet

The US on Sunday defended the downing of the Syrian jet.

"In accordance with rules of engagement and in collective self-defence of coalition-partnered forces, (the Syrian jet) was immediately shot down by a US F/A-18E Super Hornet," it said.

It said it had "contacted its Russian counterparts by telephone via an established 'de-confliction line' to de-escalate the situation and stop the firing".

It said it did did not seek "to fight the Syrian regime, Russian or pro-regime forces" but would not "hesitate to defend itself or its partnered forces from any threat".

The SDF on Monday said it would be "forced to retaliate" if the Syrian government continued attacking its positions around Raqqa.

"The regime's forces...have mounted large-scale attacks using planes, artillery, and tanks," SDF spokesman Talal Selo said in a statement.

"If the regime continues attacking our positions in Raqqa province, we will be forced to retaliate...and defend our forces."

The escalation comes as Syria's six-year-old war becomes ever more complex, with US forces and their allies converging on the northern IS bastion of Raqqa in close proximity to Russian-backed government troops.

The US-backed Syrian Democratic Forces - an alliance of Kurdish and Arab fighters - is battling to oust the militants from Raqqa, and broke into the IS stronghold city last week.

Government forces are not involved in the battle for Raqqa, but they are advancing in an area southwest of the city, skirting around SDF fighters to target Deir Ezzor.

The US-led coalition has in recent weeks escalated its aerial bombing campaign in northern Syria and Raqqa province.