The Hague: The Libyan regime of Muammar Gaddafi possessed mustard gas shells which it had not declared as a member of the Organisation for the Prevention of Chemical Weapons, the OPCW said on Friday.

A team of OPCW inspectors had visited Libya this week to check a stock of weapons discovered by the country's current rulers, the National Transitional Council, and previously undisclosed, a statement said.

"At the request of the Libyan authorities the inspectors examined munitions, mainly artillery shells, which they determined are chemical munitions and hence declarable," the OPCW said.

The shells were currently stocked at the Ruwagha depot in southeastern Libya, along with quantities of sulphur mustard and other chemicals that had been declared by the Gaddafi government but not yet destroyed, it said.

"Libya must now submit a detailed plan and completion date for destroying all of the declared materials to the OPCW not later than 29 April 2012, the date of the final extended deadline," it added.

The Gaddafi regime joined the OPCW, based in The Hague, in 2004 but had only destroyed some 45 percent of its declared stocks of chemical weapons before the destruction facility malfunctioned in February 2011, just as the ultimately successful rebellion broke out.

It still possessed 11.5 tonnes of mustard gas, not counting the undisclosed stocks discovered by the NTC last year and since formally declared to the OPCW.

(Agencies)