Somalia's Al-Qaeda-linked Al-Shabaab rebels on Monday said they carried out an attack on a town on Kenya's coast that left 49 dead.
A statement from the group said the attack in Mpeketoni, near Lamu was revenge for the "Kenyan government's brutal oppression of Muslims in Kenya through coercion, intimidation and extrajudicial killings of Muslim scholars."
It also condemned the "Kenyan military's continued invasion and occupation of our Muslim lands and the massacre of innocent Muslims in Somalia."
"To the tourists visiting Kenya we say this: Kenya is now officially a war zone and as such any tourists visiting the country do so at their own peril," the group said.
"Foreigners with any regard for their safety and security should stay away from Kenya or suffer the bitter consequences of their folly. You have been forewarned!" it added.
Around 50 heavily-armed gunmen drove into Mpeketoni, near Lamu, late on Sunday.
Witnesses said they first attacked a police station, before starting to randomly shoot at civilians, some of whom had been watching the World Cup in local bars and hotels.
The Al-Shabaab statement vowed more attacks would follow.
"We hereby warn the Kenyan government and its public that as long as you continue to invade our lands and oppress innocent Muslims, such attacks will continue and the prospect of peace and stability in Kenya will be but a distant mirage. Do not ever dream of living peacefully in your lands while your forces kill the innocent in our lands," it said.
Kenyan troops crossed into southern Somalia in 2011 to fight Al-Shabaab, later joining the now 22,000-strong African Union force battling the militants.