Updated

Britain's U.N. ambassador says the Russians and Syrians must uphold their promises to let chemical weapons inspectors visit the site of a suspected poison gas attack in the Damascus suburb of Douma — and "it should happen expeditiously."

Karen Pierce said in an interview with The Associated Press on Thursday that "it's incumbent upon them more than ever to allow the team in, to escort it, to make sure it's safe, and to make sure it can do its work."

A U.N. security team preparing the way for the inspectors was shot at Tuesday while in Douma.

Pierce says the Russians control Douma and "it has to be a possibility" they have tampered with evidence from the attack. "But," she adds, "I stress we don't yet have the facts."