Tourists were being warned to avoid large parts of Tunisia as the threat of terrorism in the country heightened.
The warning, issued by the Foreign and Commonwealth Office (FCO), follows attacks by dissidents, who reportedly killed 14 soldiers and injured 20 more in the Chaambi Mountains in the far west of the country, near the Algerian border.
The popular holiday destination attracted more than 400,000 British tourists last year, but travelers were being warned to be "extra vigilant".
An FCO spokesman said: "Our advice makes clear that there is a high threat from terrorism in Tunisia.
"We continue to advise against travel to the Chaambi Mountain National Park area."
Other areas to avoid included the towns of Nefta, Douz, Medenine and Zarzisj, and to within 30km of the border with Algeria from south of the town of Ghardinaou.
Four Tunisian police were killed when gunmen opened fire on the interior minister's family home in the western Kasserine area of Tunis, an official with the ministry said.
The minister was not at home during the attack, Mohammed Ali Laroui, a ministry spokesman said.
No group immediately claimed responsibility, but Tunisian forces are engaged in a crackdown on the hardline Islamist group Ansar al Sharia.
A military rescue plane has crashed near the Tunisian capital, killing all 11 crew on board after an engine failure, the TAP state news agency said.
The Antonov aircraft crashed in the early hours on Friday, after the pilot tried to land in farmland near Grombalia town south of Tunis, the agency said.
Tunisian President Moncef Marzouki and the head of the National Assembly have signed the country's new constitution, officially adopting a charter that is one of the country's last steps to full democracy after a 2011 uprising.
A would-be suicide bomber who tried to blow himself up at the tomb of Tunisia's former president has been captured by police, a security source told Reuters.
Earlier, a suicide bomb blast hit a hotel in Sousse, Tunisia, a police source told the news agency.
Tens of thousands of Tunisians crowded the streets of Tunis to demand the government's ouster, in the largest opposition protests to hit the capital since the country's political crisis began two weeks ago.
The secular opposition is trying to topple the Islamist-led government and dissolve a transitional Constituent Assembly that is only weeks away from finishing a draft constitution and new election law.
The protest marks the six-month anniversary of the assassination of leftist politician Chokri Belaid, one of two opposition figures to be shot dead in recent months.
Tens of thousands of Tunisians have hit the capital's streets to show support for the country's Islamist-led government in one of the largest demonstrations seen since the 2011 revolution.
Ennahda, the ruling moderate Islamist party, called on supporters of the embattled government to show their voice after a week of mass protests calling for its toppling.
The crowds responding, shouting "No to coups, yes to elections," as they filled Kasbah Square next to the prime minister's office in Tunis.
Tunisian police fired teargas to disperse violent protests in the southern town of Sidi Bouzid, cradle of the country's revolution and hometown of slain opposition figure Mohamed Brahmi, witnesses told Reuters.
Angry demonstrators, who came out to protest Thursday's assassination of Brahmi, threw rocks at police, said local resident Mahdi al-Horshani.
"Hundreds of protesters lit tyres on fire to block roads and they threw rocks at the police," he said. "There is a lot of anger and frustration at the situation."
Protesters in Tunisia have clashed with riot police near the parliament building in Tunis.
Police fired tear gas to disperse demonstrations calling for the dissolution of the assembly and Islamists defending the legitimacy of their rule.
Earlier, tens of thousands of Tunisians turned out for the funeral of assassinated secular politician Mohamed Brahmi.
Tens of thousands of Tunisians have turned out for the funeral of assassinated secular politician Mohamed Brahmi and called for the Islamist-led government to be toppled.