France has said a "reaction with force" could be needed if Syria is proved to have used chemical weapons against its own people.

The comments from Foreign Minister Laurent Fabius come as Syrian activists say hundreds of people were killed in such attacks in Damascus on Wednesday.

The UN has asked Syria to allow UN weapons inspectors already in the country to be allowed to investigate.

There is no sign as yet that Damascus will allow this.

The UN weapons inspectors are staying about 15km (10 miles) from the site of the recent attacks, but only have a mandate to visit three sites previously agreed between the UN and the Syrian government.

UN Secretary General Ban Ki-moon believes the attacks "need to be investigated without delay", his spokesman Eduardo del Buey said on Thursday.

Mr Ban was sending his disarmament chief Angela Kane to Damascus to press for an investigation, his spokesman added.

The Syrian government has described the latest allegations as "illogical and fabricated". The Syrian army said opposition forces had made up the claims to divert attention from their recent huge losses.

Heavy shelling has continued in the area on Thursday.
'Red lines crossed'

Mr Fabius told the French BFM TV channel that if the attack was confirmed, "France's position is that there must be a reaction, a reaction that could take the form of a reaction with force".

He did not elaborate on his comments, but he did rule out the use of troops on the ground in Syria.

US intelligence was urgently gathering information on what had happened, the state department said. If President Bashar al-Assad's government was found to be behind a chemical weapons attack it would be "an outrageous and flagrant escalation", a spokeswoman said.

The British Foreign Office said in a statement that the UK and 36 other countries had formally referred the latest allegations to Mr Ban, and called for inspectors "to be granted the necessary access to enable their investigation into these latest allegations as a matter of urgency".

"We believe a political solution is the best way to end the bloodshed," said the statement, but added that the UK has "said many times we cannot rule out any option... that might save innocent lives in Syria".

Turkish Foreign Minister Ahmet Davutoglu also stressed the need for an urgent response, and criticised the lack of UN action.

On Wednesday, the UN Security Council failed to agree on a statement condemning the attack at an emergency meeting.

It was blocked by China and Russia, which have repeatedly backed the Syrian government since the crisis began.

Russia did support calls for an investigation, but did so because it believes the opposition might have carried out the attack on itself, as "premeditated provocation", in an attempt to win the backing of the UN.

The weapons inspectors arrived in Damascus on Sunday with a mandate to investigate three locations including the northern town of Khan al-Assal, where some 26 people were killed in an alleged chemical attack in March.

The US has expressed its "deep concern" and urged the UN to "urgently investigate" the alleged attacks, which came a year after US President Barack Obama warned that the use of chemical weapons would cross a "red line".
Disturbing footage

Opposition activists said that more than 1,000 people were killed after government forces launched rockets with toxic agents into the Damascus suburbs in the Ghouta region early on Wednesday.

The BBC has been unable to independently confirm the death toll.

Activists said Wednesday's attack took place as part of heavy government bombardment in the region surrounding Damascus, with government forces trying to drive out rebel forces. The areas affected included Irbin, Duma and Muadhamiya.

Video footage shows dozens of bodies with no visible signs of injuries, including small children. Other videos show people being treated in makeshift hospitals, with victims, including many children, having convulsions.

While it is not clear how many died in the bombardment of the sites and how many deaths were due to any exposure to toxic substances, experts say it would be almost impossible to fake so many dead and injured including children and babies.

Both the rebels and government forces have accused each other of using chemical weapons throughout the 28-month conflict.

Syria is believed to have large undeclared stockpiles of mustard gas and sarin nerve agent.

The government has implied it has chemical weapons, but said they would not be used against civilians.

BBC