BRUSSELS - Britain has told the Syrian government that any use of chemical weapons would have "serious consequences," British Foreign Secretary William Hague said on Tuesday, adding to a series of warnings from world powers.

Hague was talking after Syrian forces bombarded rebel districts near Damascus in a counter-attack aimed at stemming rebel gains around President Bashar Assad's power base.

International concern over Syria's intentions has been heightened by reports that its chemical weapons have been moved and could be prepared for use.

"We have become more concerned about them (chemical weapons) in recent days, for the same reasons the United States has," Hague told reporters on the sidelines of a meeting of NATO foreign ministers in Brussels.

"We have already sent our own clear private message to the Syrian regime - directly to them - about the serious consequences from the use of such weapons."

US President Barack Obama said on Monday that Assad would be held accountable for any used of chemical weapons against opposition forces.

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