France’s foreign minister has threatened further missile strikes against Syria if Bashar Assad’s government uses chemical weapons again.

France joined the United States and Britain in a joint operation to destroy what French foreign minister Jean-Yves Le Drian said is a “good part” of the Syrian government’s chemical weapons arsenal.

He said France has “no doubt” that the Syrian government was behind a suspected chemical attacks last weekend. Syria denies responsibility.

French defence minister Florence Parly and foreign minister Jean-Yves Le Drian give an official statement (AP)French defence minister Florence Parly and foreign minister Jean-Yves Le Drian give an official statement (AP)

Mr Le Drian told BFM television that the goal for the allied mission had been attained, but that if France’s “red line” is crossed again there could be another attack.

Earlier, the French government said it has no samples of the chemical weapons it believes were used in Syria, but launched its military response based on open-source information and intelligence gathering.

France has released its assessment of what happened in the Syrian town of Douma on April 7 – which was the basis for France’s involvement in the joint military operation with the US and UK.

The assessment cites “the absence to date of chemical samples analysed by our own laboratories”. It said the government evaluated publicly available information from nongovernmental organisations and other sources as well as unspecified French intelligence.

It concludes that there is “no plausible scenario other than that of an attack by Syrian armed forces”.

The assessment notes eight chlorine attacks ahead of the “major attack” on Douma and 44 allegations of chemical weapons use in Syria over the past year.

Meanwhile, Germany’s chancellor said the air strikes are a “necessary and appropriate” response to the attack on Douma.

Angela Merkel said the US, Britain and France “took responsibility in this way as permanent members of the UN Security Council”.

Mrs Merkel said the strikes were needed “to maintain the effectiveness of the international rejection of chemical weapons use and to warn the Syrian regime against further violations”.

She had said earlier this week that Germany would not join allied military action against Syrian government forces.

The European Commission’s president said those who rely on chemical warfare must be held to account by the world.

Jean-Claude Juncker said the suspected use of poison gas last week in the Syrian city of Douma was — as he puts it — a “heinous chemical weapons attack carried out by the Syrian regime”.

Mr Juncker said the world “has the responsibility to identify and hold accountable those responsible” for that kind of attack.