Russian Foreign Minister Sergei Lavrov on Thursday called for the United Nations' chemical weapons watchdog to send an international group of inspectors to investigate an alleged toxic gas attack in Syria last week.

"Today there is an emergency meeting of the OPCW Executive Council in the Hague and we have sent our proposal to form such a delegation," Lavrov said at a press conference. He was referring to the Organization for the Prohibition of Chemical Weapons, an international body for chemical weapons control.

The diplomat suggested that the group of inspectors should include experts from Western countries, countries in the Middle East and Russia.

The investigation should be carried out "transparently, independently and professionally" both in the airbase where the Syrian aircraft allegedly carrying chemical weapons took off, and in the area where the alleged toxic gas was used, Lavrov said.

The United States and its allies accused Damascus of gassing civilians on April 4, but Russia said the intoxication was possibly caused by the explosion of chemical weapons produced and stored by the rebels in a local depot during a raid by the Syrian Air Force.

On Wednesday, Russia vetoed a U.N. resolution drafted by the United States, Britain and France demanding that the Syrian military provide unfettered access for UN investigators to details of their operations on the day of the alleged attack.

U.S. Ambassador to the UN Nikki Haley criticized Russia for denying the UN-led investigation and blocking a resolution that would have helped promote peace in Syria.

Lavrov, however, said at Thursday's news conference that the vetoed proposal was formulated "unilaterally" as it only asked the Syrian government to open access to all its military facilities.