"(They) should stay in their resorts and limit travel beyond their respective security perimeters". "You should follow local advice, including restrictions in selected areas", the Foreign Office said.
The country's prime minister decide to issue a state of emergency and put security services and troops on the street to tackle the gunmen after a record 335 murders past year in the area.
On Thursday the country's prime minister, Andrew Holness, said the state of emergency was "necessary" in order to "restore public safety" in the St James area.
The Jamaica Gleaner reports Major Basil Jarrett of the Jamaica Defence Force as saying: "It is in response to the rampant criminality - the murder rate, the extortion, the general lawlessness in Montego Bay".
Violent crime has been reported in Montego Bay, Kingston and Spanish Town.
It adds: 'Travel to and from the airport or for excursions should be undertaken with organised tour operators, and transport should be arranged or provided by the resort hotels'. Montego Bay, in St. James Parish, is a popular destination for global tourists."I have been advised by the security forces, in writing, that the level of criminal activity experienced, continued and threatened, is of such a nature and so extensive in scale as to endanger public safety", Holness said, according to a government news release.More news: High winds for Wales and England, more snow in the north
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The US government warns its citizens to avoid parts of Montego Bay, where "violence and shootings occur regularly".
"Violent crime, such as home invasions, armed robberies, and homicide, is common".
More than a million Americans vacationed in Jamaica in 2016, according to the latest figures from the Jamaican Tourism Board, with the island one of the top destinations for US tourists.
Police Commissioner George Quallo said 335 murders were recorded in St. James past year, nearly twice as many as in any other parish.The same day the state of emergency was announced, the UK Foreign Office, saying it would "lead to more intensive law enforcement activities".
This year, an increase in killings has increased from 23 to 38, compared to 2017.