London - Britain on Wednesday urged all sides in Zimbabwe to refrain from violence and said the situation was "very fluid" after the military took control of the country."At the moment it's very fluid and it's hard to say exactly how this will turn out," Foreign Secretary Boris Johnson said ahead of a formal statement in parliament.Britain, the former colonial power, also changed its travel advice for Zimbabwe on Wednesday.It called on Britons in the country "to remain safely at home or in their accommodation until the situation becomes clearer"."I think the most important point to make is that everybody wants to see a stable and successful Zimbabwe."I think we are really appealing for everybody to refrain from violence. That's the crucial thing," Johnson said.Britain's acting ambassador to Zimbabwe Simon Thomas said in a video statement that "any British nationals who are here in Harare, either living or working or visiting, is to stay at home, stay in your hotel room, wait until things settle down a little bit."Zimbabwe's military was in control of the country on Wednesday as Mugabe said he was under house arrest, although generals denied staging a coup.Mugabe's decades-long grip on power appeared to be fading as military vehicles blocked roads outside the parliament in Harare and senior soldiers delivered a late-night television address to the nation.Mugabe was once heralded as a liberator who rid the former British colony Rhodesia of white minority rule but was soon cast in the role of a despot who crushed political dissent and ruined the economy.