By Aaron Maasho and Duncan Miriri
NAIROBI, Oct 24 (Reuters) - Two grenade blasts killed one person and wounded more than 20 in Nairobi on Monday, two days after the U.S. embassy warned of an imminent attack as Kenya fights Islamist rebels in Somalia.
A grenade was thrown into a bar early in the morning, wounding 13 people, and police said a second device was thrown at a bus terminal in the capital just before 8 p.m. (1700 GMT), killing one person and leaving eight in a critical condition.
"There was an explosion but I thought it was a tyre burst. When I looked around I saw about eight or nine bodies. One was bleeding from his neck. He clearly had breathing problems," witness Elias Ndungu told Reuters.
A security official at the scene, who declined to be named, said the grenade may have been thrown from a passing car.
The Kenya Red Cross said one person was killed and 13 had been rushed to hospital, eight of whom were in a critical condition. The bar attack wounded 13 people, though most had been treated and discharged by Monday evening.
Kenyan Police Commissioner Mathew Iteere said earlier on Monday there was no firm evidence yet to link the first attack to Somalia's al Shabaab rebels and senior officials from the group declined to comment on either blast.
Al Shabaab had threatened major reprisals if Kenyan troops did not leave the anarchic Horn of Africa nation and they have launched large-scale attacks in the past in Somalia and Uganda, for which they have quickly claimed responsibility.
Al Shabaab warned Burundi on Monday to pull its soldiers out of Somalia, where they are fighting the rebels alongside Ugandan soldiers in a 9,000-strong African Union force.
Nairobi blames al Shabaab for a series of kidnappings of foreigners on Kenyan soil that has threatened the country's multi-million dollar tourism industry. The group has denied responsibility for the kidnappings, saying Nairobi is using them as a pretext for its military campaign.
Kenyan troops have advanced on several fronts in southern Somalia since crossing the border just over a week ago and are nearing the strategic transit town of Afmadow, where rebels have regrouped and reinforced their defences.
Somali government officials and residents said Kenyan and Somali troops seized the town of Busaar, about 40 km (25 miles) from border town El Wak, on Monday. They said the rebels fled after a brief exchange of fire.
France denied on Monday reports that its navy had been involved in any bombardment on Saturday of the Somali town of Kuday, near the port city and al Shabaab stronghold of Kismayu. It said no French warships were in the vicinity.
The grenade attacks came two days after the U.S. embassy warned of an imminent threat of reprisals on places where foreigners are known to congregate, such as malls and clubs.
The bar attacked on Monday, however, was small, rundown and in an area where foreigners rarely go drinking.
Witnesses said a man knocked on the door of Mwaura's bar, threw in the grenade and ran away.
"I heard an explosion, there was darkness and I thought the electricity had gone out but when I touched my face, there was blood," Lawrence Kioko told Reuters.
Iteere told a news conference the device was Russian-made and similar to one that killed two people in another bus station attack last December.
Reuters footage showed blood and beer bottles on the ground of the bar, which is frequented by labourers attracted by its cheap beer and spirits. Blood stained a sink and overturned seats and debris littered the floor.
"There was a lot of blood, injuries, people were screaming, others confused, generally it was chaotic. It was a chaotic situation," bar owner Charles Mwaura told Reuters.
Iteere said the police had boosted security around potential targets within Kenya. After the second blast, police warned Kenyans to be vigilant and banned the use of fireworks during the Hindu festival of Diwali.
"The people who would like to scare us will go for targets with a large number of people and therefore any place with a large number of people we must be vigilant, we must be extra careful," Charles Owino, deputy police spokesman, told Reuters.
Iteere also said police had found a number of AK-47 rifles at the weekend in the Dadaab refugee camp in northern Kenya, home to more than 400,000 Somalis.
SOMALI GOVERNMENT NOT PLEASED
Kenya is the latest of Somalia's neighbours to intervene militarily in a country without an effective government for the last 20 years. Kenya has in the past initiated brief cross-border incursions but the latest operation is on a larger scale, raising fears the country may be dragged into its conflict.
While Somali officials had said the two countries were cooperating in the fight against al Shabaab, President Sheikh Sharif Ahmed was more circumspect about the incursion on Monday.
"The Somali government and its people will not be pleased with Kenya's intervention," Sharif told reporters while visiting the frontline in Mogadishu. "We had not agreed with Kenya beyond helping us with logistics."
The Islamist militants launched large-scale suicide attacks within Somalia and Uganda and have warned they would bring the "flames of war" into Kenya.
This month, a suicide truck bombing claimed by the rebels killed more than 70 people at a compound housing government ministries in Somalia's capital Mogadishu.
The militants also claimed responsibility for a bomb attack in the Ugandan capital, Kampala, which killed 79 people watching the soccer World Cup final last year. (Additional reporting by Yara Bayoumy, Njuwa Maina, Noor Khamis, Fouad Khoeis, David Clarke and Ben Makori in Nairobi, Abdirahman Hussein, Abdi Sheikh, Sahra Abdi and Fesial Omar in Mogadishu; Writing by David Clarke; Editing by Michael Roddy)