BEIRUT - Syrian government forces have attacked rebel-held areas with chlorine gas in recent weeks, according to interviews with more than a dozen activists, medics, and residents on the opposition side.

The U.N. Security Council called for an inquiry Wednesday as members expressed "grave concern," said Nigeria's U.N. ambassador, U. Joy Ogwu, council president.

Syria denied the allegations, and they have yet to be confirmed by any foreign country or international organization. If true, they highlight the limitations of the global effort to rid President Bashar al-Assad's government of its chemical weapons.

Witnesses near Damascus and in a central rebel-held village told the AP of dozens of cases of choking, fainting, and other afflictions from inhaling fumes that some said were yellowish and smelled like chlorine cleanser. Some of those interviewed said they believe the gas was responsible for at least two deaths.

Activists have posted videos similar, though on a far smaller scale, to those from August's chemical-weapons attack near Damascus that killed hundreds. The new footage depicts men, women, and children coughing and gasping at field hospitals.

The latest allegations come as Assad faces a Sunday deadline for handing over all his chemical weapons for destruction.

Chlorine is a potentially lethal chemical with a multitude of ordinary uses, including laundry bleach and swimming-pool disinfectant. In high concentrations, it can attack the lungs. It is no longer officially considered a warfare agent and is not among the chemicals declared by Syria. Still, any toxic chemical is considered to be a chemical weapon if used for military purposes.