MOSCOW (AFP) - Russia's deputy foreign minister Sergei Ryabkov condemned the United States on Monday (June 19) for shooting down a Syrian warplane, describing it as an act of aggression.

"This strike has to be seen as a continuation of America's line to disregard the norms of international law," Ryabkov told journalists in Moscow, according to the TASS state news agency.

"What is this if not an act of aggression?" he said in Russia's first official reaction to the downing of the plane on Sunday (June 18).

"It is, if you like, help to those terrorists that the US is fighting against, declaring they are carrying out an anti-terrorism policy," Ryabkov said.

The US-led coalition said the Syrian plane had dropped bombs on its allies fighting against the Islamic State in Iraq and Syria (ISIS) group in the war-torn country.