Wed Sep 26, 3:08 PM ET

LONDON - The government warned its citizens on Wednesday against "all but essential travel" to Myanmar as the military junta there launched a bloody crackdown on protestors.

"We advise against all but essential travel to Burma (Myanmar) due to the unsettled political situation," the Foreign Office in London said.

"Protests against the government are taking place in cities across Burma and there have been reports of clashes between protestors and the security forces," it added.

Myanmar security forces used batons, tear gas and live rounds Wednesday in a violent crackdown on the mass protests, killing at least four people including three Buddhist monks, witnesses said.

The Foreign Office added that a curfew has been imposed between 6:00 pm and 6:00 am in Myanmar's largest city Yangon and Mandalay and gatherings of more than five people have been prohibited.

The ministry had previously urged travellers to be cautious as "the political situation remains unsettled".