The US military has said it was repositioning its aircraft over Syria to ensure the safety of American air crews targeting the self-proclaimed Islamic State group.

The announcement comes as tensions escalate following the US downing of a Syrian military jet near Raqqa yesterday.

Iran also launched missiles at IS targets in eastern Syria yesterday -  the first time each state has carried out such actions in the multi-sided conflict.

The US said the downed Syrian plane had dropped bombs near fighters of the Syrian Democratic Forces, a US-backed alliance of Kurdish and Arab fighters battling to capture Raqqa from IS.

Russia's Defence Ministry responded by suspending cooperation with the US aimed at avoiding air incidents over Syria, where the Russian air force is bombing in support of President Bashar al-Assad's campaigns against rebels and IS.

The Syrian army said the jet was shot down while flying a mission against IS.

The SDF however accused the Syrian government of attacking its positions using planes, artillery and tanks.

"If the regime continues attacking our positions in Raqqa province, we will be forced to retaliate," a SDF spokesman said.

The Syrian government this month marched into Raqqa province from the west but had avoided conflict with the US-backed SDF until the latest incident.

Russia, Iran and the US are drawing new red lines for each other in Syria, with Russia warning it would treat any US-led coalition planes in its area of operations as potential targets following yesterday’s incident.

"As a result of recent encounters involving pro-Syrian Regime and Russian forces, we have taken prudent measures to re-position aircraft over Syria so as to continue targeting ISIS forces while ensuring the safety of our aircrew given known threats in the battle space," a spokesman at US Air Forces Central Command said.

The US also said they are working to restore the "deconfliction" communication line with Russia.

Marine General Joseph Dunford, the chairman of the Joint Chiefs of Staff, said there was still communications between a US air operations center in Qatar and Russian forces on the ground in Syria but added: "We'll work diplomatically and military in the coming hours to reestablish deconfliction."