The hugely popular holiday destination was visited by more than 200,000 people last year – but it has been rocked by a series of killings which has prompted the authorities to take a tough stance.
The murder rate in the St James Parish Area, which includes Montego Bay, is already double that of the rest of Jamaica, with 335 people killed last year.
In the most recent incident, a car carrying three men and a child was sprayed with bullets in a drive-by shooting just yards from Sangster International Airport on Tuesday.
Four gunmen, wielding AK-47 assault rifles, targeted the vehicle, killing the driver and injuring the other men. Miraculously, the child was unhurt.
Hours later, another man was shot four times, also near the airport, prompting Prime Minister Andrew Holness to take action.
The Foreign Office is advising all British tourists on the island to stay in their hotels, stressing the “intensive law enforcement activities in response to recent violence including shooting incidents”.
The Foreign Office said: “Tourists should stay in their resorts and limit travel beyond their respective security perimeters.
“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.
“Local media have reported that a major military operation is underway in parts of St James.
“This may result in road closures and travel delays. You should exercise caution if you’re in the area.”
Mr Holness said members of the security forces would be equipped with “extraordinary powers” to deal with the situation.
The state of emergency covers the north-western parish of St James, which includes Montego Bay, which has twice the number of murders any other parish in Jamaica.
It allows local law enforcement officials to search homes and individuals, curtail operation hours of businesses and detain suspects without warrant.
Justice minister Deleoy Chuck said: “These actions will not be done randomly. Effective communications will occur by order and in accordance with the emergence powers regulations.”
International travel expert Nick Harris of Simpson Millar solicitors, said: “UK tourists are now quite rightly concerned about outbreaks of violence and those due to fly out in the coming days are now trying to cancel their trips over safety fears.
“This is a very worrying time for tourists caught up in this war on crime.
“Armed soldiers on the streets is not what you expect to see when you land in your dream holiday destination and is very frightening.
“But what people need to know is this is a developing country with all the associated problems and with the high murder rate unfortunately life is cheap.”
Around 206,000 British travellers visited Jamaica in 2016.