Nairobi, Kenya — Police have blamed the Islamist Al Shabaab militia for a grenade attack on a Nairobi bus station Saturday that has killed at least four people and wounded more than 20 others.
"This is a cowardly act by Al-Shabaab elements," police spokesman Charles Owino told reporters at the bus station.
"But we will not relent in the war. We will get them and we will continue with the war."
Kenyan troops are currently fighting the Shabaab in neighbouring Somalia.
"We can confirm that indeed three people have been killed, 21 injured," he added.
"We have 59 people who are admitted here, eight of them are in a critical condition," Kenyatta National Hospital's Spokesman Simon Ithai told Capital News.
"Unfortunately, we have lost one person here."
This brings the death toll to four as police had confirmed three deaths.
The attack took place at the Machakos country bus station, near the city centre. Earlier, a senior police official who did not want to be named said it was believed several grenades had been thrown at the bus station.
"I just saw a vehicle pass and then someone just threw things that exploded," witness Charles Njenga said.
"Many people have been injured," he added.
"I survived because I was in a bus that was still loading people."
Other witnesses spoke of three or four grenades having been thrown in and around the bus station from out of a car.
Traces of blood were still visible on the floor of the bus station, where around 10 buses were still parked, and ambulances were still ferrying the wounded to hospital.
Other, less seriously injured people were being treated on the spot.
About 500 metres (yards) from the bus station, the body of one of the victims, a young man, could be seen was stretched out in front of a petrol station
"I came to get petrol when I saw a man who was running and he collapsed, dead," said motorcyclist Reuben Otela.
"When I got closer, I saw that he was covered in blood, he had fled the explosion," he added.
It is the first such incident in the Kenyan capital since two grenade attacks carried out within 24 hours of each other last October killed one person and injured 30 others.
The first of those attacks targeted a bar in the capital; the second was an attack on a particularly bus stop.
A Kenyan supporter of Somalia's Islamist Shabaab fighters was arrested soon afterwards and was convicted after having confessed to the attacks.
No one has so far claimed responsibility for Saturday's killings.
But the Shabaab have on several occasions threatened reprisal attacks against Kenya since it sent its troops over the border into southern Somalia in mid-October to fight the group.
Kenya sent its soldiers, backed by planes and helicopters, into Somalia following the abduction of several foreigners on Kenyan soil -- although the Shebab have denied any involvement in the kidnappings.
A month later, in November, Ethiopian troops and tanks entered Somalia to support the Somali transitional government against the Shebab.
Earlier Saturday Shabaab fighters launched a major attack lasting several hours against positions held by Ethiopian forces in southwest Somalia.
The battle left many fighters dead, witnesse and military sources on both sides told AFP.
As well as the Ethiopians and the Kenyans, the Shabaab fighters are under pressure from an African Union force of Ugandan and Burundian troops, which has forced them out of the Somali capital Mogadishu.
The Kenyan army has since last month been part of the African Union force.