The US put 271 Syrian chemists and other officials on its financial blacklist Monday (April 24th) for their presumed role in the deadly chemical weapons attack on an opposition-held town in early April, AFP reported.

In one of its largest-ever sanctions announcements, the US Treasury Department took aim at the Syrian Scientific Studies and Research Centre (SSRC), which it said was responsible for developing the alleged sarin gas weapon used in the April 4th attack.

The attack left 87 dead, including many children, in the town of Khan Sheikhun.

The sanctions will freeze all assets in the US belonging to the 271 listed individuals, and block any American person or business from dealing with them.

The centre was the subject of two earlier sanctions declarations, in 2005 and 2007, due to its alleged role in developing weapons of mass destruction.

In a Monday statement, the Treasury accused the SSRC of being behind the Syrian regime's efforts to develop chemical weapons and the means to deliver them.

The 271 individuals named either have scientific expertise for the programme or have been involved in it since 2012, the statement said.

Meanwhile, the Russian defence ministry said in a Monday statement that Syria's military is ready to halt fire around Khan Sheikhun if experts are sent in to conduct a probe.

Damascus was "ready to declare a complete moratorium on the activities of its troops, aviation and artillery in the area" if investigators were sent in, the ministry said, adding that they would be granted access to the Shayrat airbase.

The Syrian regime has not made any official announcement on the matter.