The Kenyan capital was hit Monday by two blasts apparently aimed at civilians a little more than a week after government troops were sent into the country's war-torn neighbor, Somalia.
One person was reported dead and more than 20 were injured in the attacks.
No one immediately claimed responsibility. But a spokesman for insurgents with the Shabab group last week warned that the group would cause violence in Nairobi if Kenyan troops were not withdrawn.
In the first attack, a grenade strike at a bar in downtown Nairobi early Monday injured about 12, with most suffering cuts and scratches.
About 8 p.m., a blast at a crowded bus terminal killed one person and injured 13, the Daily Nation reported. Police said the second attack may also have been caused by a grenade.
Two days earlier, the U.S. warned of the possibility of terrorist attacks in Kenya, with crowded places such as bars and shopping malls considered prime targets.
The Shabab, which controls much of southern Somalia, has carried out several major suicide attacks in the region, killing more than 80 people in bars in Uganda last year and, more recently, 80 or so outside a government compound in Mogadishu, the Somali capital.
Some analysts have warned that given Somalia's history — two decades with no functioning central government and numerous failed foreign interventions since the early 1990s — Kenya could become bogged down in a military quagmire there.
Already, troops are bogged down in a literal sense: The incursion came after seasonal rains, which turned the roads to swamps and trapped heavy military vehicles in the mud.
Kenya's military operation is aimed at preventing kidnappings of foreigners by pirates and extremists — highly damaging to the country's tourist industry — and to drive the Shabab from its main base, the port city of Kismayo, a smuggling point for weapons and contraband.
Charles Mwaura, owner of the bar attacked Monday, told The Times that the business had a small clientele.
"This incident really was a great shock to me and my staff. We didn't expect such a thing to happen at this area of the town, although we are afraid anything might happen now that the government has started the war against the terrorists from Somalia, Al Shabab," he said.
Taxi driver Moses Kamau said the message from the attackers was clear.
"I think we now know these people are up to a revenge mission and can attack anywhere in our country," he said. "We are vulnerable, and can be attacked any time. So we are in fear, and generally we think the government is not capable of stopping such attacks."
Special correspondent Soi reported from Nairobi and Times staff writer Dixon from Johannesburg.