The US embassy said on Tuesday it has been alerted to a possible terrorist threat targeting this month's world cross-country championships in Kenya.
The embassy said the threat came from "alleged extremist elements" and that the event "may be the target of an unspecified terrorist attack."
Last month, the US embassy issued another strong warning to Americans considering a visit to Kenya, saying violent crime was increasing and that Kenyan authorities have limited capacity to prevent it.
"The US embassy is also aware of public statements by leaders of Kenya's coastal Muslim community threatening to disrupt, through unspecified means, the World Cross Country Championship if the government of Kenya does not satisfy various demands," Tuesday's statement said.
No further details were released and embassy spokeswoman Jennifer Barnes said she had no further comment.
Isaac Kalua, head of the race organizing committee, said there was no security problem.
"An act of God can disrupt [the race], but we have an able security personnel who would do everything to guarantee the safety of the participants," Kalua said.
The International Association of Athletics Federation's (IAAF) World Cross Country Championships are scheduled for March 24 in the coastal city of Mombasa. There are men's and women's senior and junior races. Athletes from 66 countries are expected to compete in the championships, which are being held in Kenya for the first time.
The IAAF said in a statement that Kenyan authorities assured the group on Tuesday that "a specific security plan, involving all branches of the country's military and police authorities, is already in place to protect all athletes and participants during their stay in Kenya."
Muslim leaders in Mombasa in recent weeks have threatened to disrupt the event unless the government releases Kenyans held on suspicion of engaging in terrorism and those detained in Somalia and Ethiopia. The protests were led by Sheik Mohamed Dor, secretary-general of the Council of Imams and Preachers of Kenya.
Dor said on Tuesday his group will disrupt the races unless the detainees are released, but that there will be no violence.
"We are going to have a very, very big demonstration to disrupt the cross country," he told the press. "[Members of] every international media [organization] will be in Mombasa, so we want to show the world that Kenyan Muslims are marginalized."
Kenya has been the victim of terrorism in the past. In 1998, terrorists bombed the US embassies in Nairobi and Dar es Salaam, Tanzania, killing 225 people. Kenya was also the site of a car bomb at a beach resort and the near simultaneous attempt to shoot down an Israeli airliner in 2002. Ten Kenyans and three Israelis were killed in the blast at the hotel, 20km north of Mombasa. The missiles missed the airliner.
The men's race will feature Ethiopian great Kenenisa Bekele, who will be going for his 11th world cross country title and sixth long course victory in a row. Bekele, who swept the short and long course races at the past five championships, said last year he would not compete in the event again because there was nothing left to win.
However, Bekele announced on Monday that he had changed his mind and will run in Mombasa, where he will seek to become the first runner to win six consecutive long-course titles.