- NEW: The Red Cross says 24 people are admitted to a Mombasa hospital
- The group reports 2 grenade attacks -- one in Mombasa, one in nearby Mtwapa
- 2 of those injured are in critical condition, a Kenyan intelligence official says
- Other nations have warned in recent months about possible terrorism in Kenya
Nairobi, Kenya (CNN) -- A pair of grenade attacks rocked southeastern Kenyan Saturday night, killing one person and injuring at least 15 others, according to the Red Cross and a Kenyan intelligence official.
Two of 15 people hurt were in critical condition at a local hospital, said the official, who asked not to be named.
The Kenya Red Cross, on its official Twitter feed, similarly reported a single fatality as a result of a grenade attack in the coastal town of Mtwapa, which is about 15 kilometers (9 miles) northeast of the city of Mombasa.
A different, "twin grenade attack" occurred around the same time -- about 7:30 p.m. (12:30 p.m. ET) -- at Tononoka Stadium in Mombasa itself, according to the Red Cross.
The non-profit organization originally reported that at least one person was injured in that attack, in addition to 16 hurt in Mtwapa.
But a short time later, the Red Cross tweeted that 24 people had been admitted to Coast General Hospital in Mombassa, two of them in intensive care.
The attacks occurred in the communities along the Arabian Sea, about 480 kilometers southeast of Nairobi, the intelligence official said.
It was not immediately clear if anyone had claimed responsibility.
The East African nation has been on edge since it sent its troops into Somalia to pursue Al-Shabaab militants after the abductions of tourists and aid workers in Kenya. It blames the abductions on Al-Shabaab, which has denied involvement.
Al-Shabaab, which the United States considers a terror group, has threatened to attack Kenya if it does not withdraw its forces from Somalia.
In January, Britain's Foreign and Commonwealth Office said in a statement that "we believe that terrorists may be in the final stages of planning attacks" in Kenya.
U.S. Embassy officials in Kenya issued their own terror alerts last October and November, saying they had credible information of an imminent terror attack.
CNN's David McKenzie and Journalist Boniface Mwangi contributed to this report.