Britain's foreign secretary says the country will ask the United Nations Security Council to discuss claims of a chemical weapons attack near the Syrian capital, Damascus.

Syrian opposition groups say at least 100 people were killed during a fierce government offensive against rebel-held areas, and some activists say regime troops used "poisonous gas."

The Syrian government denied its troops used chemical weapons.

Britain's Hague said Wednesday that "if verified, this would be a shocking escalation of the use of chemical weapons in Syria. We are determined the people responsible will one day be held to account."

He said U.N. chemical weapons inspectors, who are currently in Syria, should be given access to the site.

[Associated Press]