A British government official confirmed the asylum request to The Associated Press earlier Friday. The official spoke on condition of anonymity because he was not authorized to talk to the press. Other British media outlets cited police.
The male Olympian allegedly appeared Tuesday night at a police station in the northern English city of Leeds, the training camp base for several countries' Olympic teams, including Sudan.
"We herewith categorically refute allegations ... that a Sudanese member of those who qualified for the Olympic competition and have arrived in London is either missing (or) sought political asylum," the Sudanese Embassy said in a statement.
Sudan's Embassy was closed when the statement was issued and not accepting phone calls. Embassy officials did not respond to AP emails seeking comment.
An official identifying himself as the mission chief of Sudan's Olympic Committee declined to comment when reached by telephone. The official also declined to give his name.
The alleged asylum seeker's name likewise has not been disclosed. But the British official told the AP he was competing as an 800-meter runner.
Only two Sudanese runners are competing at that distance: Abubaker Kadi and Ismail Ahmed Ismail, who is supposed to be his country's flag bearer for Friday's opening ceremony.
Ismail, a 28-year-old from the Sudanese capital, Khartoum, is Sudan's only Olympic medallist in history. He won a silver in the 800 metres at the Beijing Games in 2008.
Kadi is a 23-year-old from Elmuglad, Sudan.
International Olympic Committee President Jacques Rogge said Friday he knew of a reported asylum request but had not independently verified the details. "I know about the fact there has been a request but I don't know the decision of the government," Rogge said.
The Home Office, the government agency responsible for law and order in England, refused to comment.
The mostly black African tribes in southern Sudan and the country's mainly Arab north fought two civil wars over more than five decades. Some 2 million people died in the latest 1983-2005 war. That conflict ended with a peace deal that culminated in last year's independence declaration for South Sudan.
Although that breakup was peaceful, tensions have flared this year between Sudan and South Sudan over their border, competing rights to oil revenues and other contentious issues. Rebel groups that support South Sudan's ruling party still seek to topple Sudan's government in Khartoum.
Associated Press writer Graham Dunbar in London contributed to this report.