At least 48 people were killed and others wounded when more than two dozen unidentified gunmen attacked a coastal Kenyan town overnight, police and the Kenya Red Cross said on Monday.
The attackers targeted two hotels, a bank and a police station with guns and at least one explosive device on Sunday night.
There was no immediate claim of responsibility. Police said the gunmen could have been Islamist militants or criminals.
The assault was the latest in a string of gun and bomb attacks that have hurt Kenya's vital tourist business and which have been blamed on Somalia's Al Shabaab militant group. Western nations have issued travel warnings in the wake of the assaults.
Sunday's toll is the highest since 67 people were killed in an attack in September on Nairobi's Westgate shopping mall. That raid was claimed by Al Shabaab, which said it wanted to force Kenya to withdraw troops from Somalia. Kenya has said it won't.
"More bodies have been recovered and right now we are talking about 48 dead persons," Leonard Omollo, Lamu County police commander, told Reuters on telephone.
"All the dead are men. There are no women or children, and this fairly complicates matters. We may not tell immediately whether the attacks were done by Al Shabaab, the MRC (Mombasa Republican Council) or just mere criminals," Omollo said.
The MRC is an illegal movement that wants the coastal region to secede. It has not recently been linked to attacks of this scale. Since the Westgate attack, Al Shabaab have promised to strike again.
The Kenya Red Cross said some of the casualties had been evacuated to a hospital in Lamu, a popular tourist destination that lies about 30 km (20 miles) away. It is situated along the long coastline that runs north from Mombasa port to Somalia.
Those killed include a policeman who worked as a driver for a police chief in the towns, said David Kimaiyo, the inspector general of Kenya's police. Many Mpeketoni residents had fled from the attack into nearby forests, he said.
"We have not arrested anybody in connection with the attack so far," Kimaiyo said.
A Reuters television reporter in the town saw at least six bodies strewn on roads inside the town. Ten burnt-out vehicles were also seen in the area and a Kenyan bank branch was gutted in the attack, the reporter said.
Residents said there were at least 30 attackers who used two vehicles in the raid.
Two military helicopters flew over the town on Monday morning, the Reuters witness said.
Mpeketoni is about 130 km (80 miles), or more than three hours' drive along poor roads from the border with Somalia, where Kenya forces have joined an African peacekeeping force fighting al Shabaab militants.