Britain's Prime Minister Theresa May speaks during a media conference with Danish Prime Minister Lars Lokke Rasmussen, at Christiansborg Castle in Copenhagen, Monday April 9, 2018. (Mads Claus Rasmussen/Ritzau Scanpix via AP)

COPENHAGEN - The Syrian regime "and its backers, including Russia, must be held to account" if the government is found to be responsible for a suspected poison gas attack in the country, British Prime Minister Theresa May said Monday.

May said those who back "the brutal actions by (Syrian President Bashar) Assad and his regime ... they need to look very carefully at the position they have taken."

"The events in Douma fit into a troubling wider pattern of acts of aggression and abuse of long-standing international norms on counter-proliferation and the use of chemical weapons," she told reporters. "In recent years Russia's repeated vetoes and the U.N. have enabled these rules to be broken and removed mechanisms that allow us to investigate and hold to account chemical weapons attacks in Syria. This must stop."

She calls Saturday's suspected attack on the besieged town of Douma "a reprehensible attack," adding Britain is in talks with its allies about "what action is necessary."

At a later news conference in Sweden, May declined to explicitly rule out joining an international coalition that might consider military action if the regime of Syria's president is determined to be responsible for the Douma attack.

But she stressed Britain is still gathering the facts.

May drew a parallel with a military-grade Soviet-made nerve agent poisoning on a former Russian spy and his daughter, for which Britain blames Russia, saying "we saw a similar recklessness" in the use of chemical weapons in the English city of Salisbury on March 4. Russia has denied responsibility for the attack.

Sergei Skripal and his daughter Yulia were found unconscious and were taken to a hospital, where for weeks they lay unconscious in critical condition. The condition of the ex-spy is improving rapidly and he is no longer in critical condition, while Yulia Skripal regained consciousness last week and is now in stable condition.

May said Britain is considering taking further action against Russia.

After meeting with her Danish counterpart Lars Loekke Rasmussen during a visit to Copenhagen, May called Syria "a brutal regime that is attacking its own people and we are very clear that it must be held to account."

News from © The Associated Press, 2018