The move followed a deadly US air strike on the Shayrat airfield of the Syrian air forces, believed by Washington to be the base for warplanes that carried out the chemical attack. (Photo: AP)

Washington DC: Russia has formally notified the United States of suspending a communications hotline with the Pentagon over the Syria chemical attack row starting Saturday, a spokesman for the US Department of Defense told TASS news agency.

Defense Ministry Maj. Gen. Igor Konashenkov said Friday that Russia was suspending the communications channel which the two sides established in line with a memorandum of understanding on prevention of incidents and ensuring of flight safety in Syrian airspace.

"The US military attache in Moscow was summoned to the Defense Ministry to get an official note, which said the Russian side was suspending as of 00:00 hours on April 8 the observance of its obligations under the memorandum of understanding on prevention of incidents and ensuring of flight safety in the course of operation in the Syrian Arab Republic," he said.

The move followed a deadly US air strike on the Shayrat airfield of the Syrian air forces, believed by Washington to be the base for warplanes that carried out the chemical attack on a rebel-held town on Tuesday that killed at least 80 people.

Russian President Vladimir Putin denounced the strike as "act of aggression" and said it violated international law.

Russia earlier this week denied a chemical weapons attack took place in Syria saying the deaths in Khan Sheikhoun were caused by a Syrian regime airstrike on a rebel-controlled chemical weapons factory on the ground.