The Shabab on Monday claimed responsibility for an attack the day before that killed at least 48 people, marking the first time the militant group from Somalia had launched an assault of this scale on a town in neighboring Kenya.
Witnesses reported that the attackers in the town of Mpeketoni spoke Somali and yelled "God is great." Kenyan authorities earlier said they suspected the Al Qaeda linked militants were to blame.
The group released a statement saying its fighters burned a police station, bank, hotels and other buildings in revenge for the killings of several clerics in the Kenya city of Mombasa and the continued presence of Kenyan troops in Somalia.
In a chilling warning, designed to exact maximum damage on Kenya's tourist industry, the group declared the country a war zone and warned foreigners to stay away.
The statement, reported in Kenya's media, said the militia had control of the town for 10 hours before withdrawing "leaving behind a rail of destruction and scores dead."
"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 statement said. "Foreigners with any regard to their safety and security should stay away from Kenya or suffer the bitter consequences of their folly."
It warned of more attacks in future: "Do not ever dream of living peacefully in your lands while your forces kill the innocent in our lands," the statement said.
Dozens of gunmen hijacked two buses and swept into the town as local people watched the World Cup soccer competition in a video hall. Gunmen invaded hotels and homes, shooting the one police officer present and killing civilians on sight.
Some 50 gunmen were reportedly involved. The attack, 60 miles from the border – a porous, poorly guarded line in the scrub - underscored how poorly secured most of Kenya is, despite a three-year terror campaign by Al Shabab since Kenya invaded Somalia in 2011.
It suggested growing sophistication for such a large group of heavily armed gunmen to have penetrated so deep into Kenya undetected before carrying out a military-style attack on the town. Past attacks have involved bombings, grenades and assaults by smaller groups of gunmen such as last year's attack on the upscale Westgate shopping mall in Nairobi.
After a series of 2011 kidnappings by Somali gunmen, Kenyan forces invaded Somalia that year to improve security in northern Kenya, protect their country's valuable tourist industry and prevent Shabab militants from penetrating into Kenyan territory. However, Sunday's attack provided stark evidence that the attempt to create a buffer zone separating Somalia from Kenya had not succeeded.
Cedric Barnes, Somalia analyst with the International Crisis Group, said that although attacks had been ongoing since 2011, the Shabab and its affiliates had never carried out an assault on a Kenyan town involving so many gunmen.
"You have seen an increased tempo in the last 12 months, but nevertheless they have never done something quite as direct in terms of a group of armed people attacking a specific town, so far from the Somali border, and shooting civilians," he said.
"Ultimately it's showing the consequences for Kenyan intervention in Somalia and it's sowing divisions between different groups in Kenya," he said. "It goes to show how thinly spread Kenyan security forces are and how poorly secured large parts of Kenya are."
He said there had been a constant exchange of training and information between the Shabab and allied extremist groups in Kenya and elsewhere. Six months ago Shabab leaders in Somalia ordered non-indigenous militias training in Somalia to return to their home countries to carry out attacks, according to Barnes.
Stig Hansen, author of "Al Shabab in Somalia: The History and Ideology of a Militant Islamist Group, 2005-2012," said the attack underscored Kenya's failure to improve its intelligence and investigations since last year's attack on the Westgate shopping mall in Kenya's capital carried out by four Shabab gunmen, which killed at least 68 shoppers.
In recent months, amid a series of grenade attacks and bomb blasts, Kenyan security forces have carried out random sweeps in the Eastleigh neighborhood where many ethnic Somalis live, some of them Kenya-born. Thousands of people have been rounded up and hundreds deported in operations criticized by human rights groups.
Hansen said that since the
"I haven't seen any progress in these areas. In fact I've seen the opposite," he said. "What we've seen is a repeat of old patterns of collective targeting and arrests of Somalis."
Hansen said Sunday's attack bore the signs of other Shabab operations, including its carefully planned assaults on soft targets and its attacks in the northeast of the country designed to hit Kenya's tourist industry.
Although Mpeketoni is not a tourist town, he said the attack was close to a tourist site, Lamu.
"It's an ongoing war between Shabab and Kenya," Hansen said. "They will hit Kenya where it hurts, in tourism or any other areas where they can score points."
Kenya relies on tourism as one of its major income sources. It recently suffered a setback when British tourism companies evacuated several hundred tourists from coastal Kenya after travel warnings from the U.S. and British governments about a heightened danger of terror attacks.
Barnes said Kenya could no longer assume that terrorists in Kenya were just ethnic Somalis, with the rise of several local groups, trained by Shabab, which included Kenyan converts to Islam.
"We know there's been a good deal of internal radicalization of people here who are not necessarily Somali. Many of the mosques that were radicalized in Mombasa are not Somali-dominated mosques," he said, referring to the coastal port that has seen unrest, particularly after the killings of several radical preachers that sparked riots in recent years. Local communities have blamed Kenyan authorities for the killings.
Sunday's attack follows a new offensive by the U.N.-backed African Union troops in Somalia, AMISOM, including airstrikes by Kenyan forces, driving Shabab out of several towns since March. Barnes said Shabab had proved extremely resilient, fighting back, attacking towns, regaining territory and forcing the African Union force out of some areas, while carrying out terror attacks in major towns, including Mogadishu.
"They're present everywhere in most areas of south-central Somalia," he said. "They seem to be able to hit wherever they like."