ISLAMABAD, Pakistan (CNN) -- An Arab man detained by Pakistani authorities the day bombs gutted U.S. embassies in Kenya and Tanzania has acknowledged being a member of a team recruited by renegade Saudi millionaire Osama bin Laden to bomb the Kenya embassy, The Washington Post reported Monday.

Sources at four Pakistani police and intelligence agencies told the Post that Mohammad Sadiq Howaida, 34, was turned over to U.S. officials in Islamabad three days ago. Other sources told the paper that American officials flew from Pakistan to Kenya with Howaida on Saturday and arrived there Sunday.

Meanwhile, the Pakistani national newspaper The News, quoting unnamed sources, said Howaida gave a calm and detailed confession to Pakistani interrogators about having helped plan the bombings in East Africa as part of an Islamic crusade against the United States.

The News also reported that Howaida said the attacks were sponsored by bin Laden, a known sponsor of terrorism and vowed enemy of the United States who is harbored in Afghanistan. U.S. officials have identified bin Laden as a possible suspect in the bombings.

The nearly simultaneous bombings on August 7 at the embassies in Nairobi, Kenya, and Dar es Salaam, Tanzania, killed 257 people, including 12 Americans. Sources told the Post that Howaida expressed regret that more than 200 non-Americans were killed.

During two days of questioning by Pakastani authorities, the Post reported, Howaida claimed he had provided technical, engineering and logistical support for the Kenya bombing. Sources told the Post that Howaida said he had been one of seven operatives in Nairobi for bin Laden.

The operatives traveled from Afghanistan to Nairobi, the Kenyan capital, some time ago, prepared the bomb and then flew to Karachi just prior to the bombing, the Post reported. Howaida said the operatives were carrying passports from various countries and that the other six slipped by inspectors at the Karachi airport, the Post said.

According to the Post, Howaida said the operatives had expected to be greeted and thanked by bin Laden after returning to Afghanistan through Pakistan.

In a brief statement Sunday, Pakistani Foreign Ministry spokesman Tariq Altaf confirmed Howaida arrived at the Karachi airport from Nairobi on the day of the bombings. Immigration officials determined Howaida's Yemeni passport was forged, and he was interrogated by Pakistani officials who determined he had some link to the embassy bombings.

"On satisfaction about his involvement in these terrorist acts, he was sent back to Nairobi and handed over to the Kenyan authorities for appropriate action under their law," Altaf said, adding that Howaida was sent to Nairobi aboard a special Pakistani plane. Altaf did not say when Howaida was returned.

News of the detainment comes as U.S. Secretary of State Madeleine Albright is scheduled to leave Washington Monday for visits to Kenya and Tanzania as a show of support for those countries and to express condolences to the victims.

The circumstances surrounding Pakistan's handling of the case remain unclear. The News reported that one of its sources said Howaida was handed over to U.S. officials who took him to an undisclosed location, while another source told the news he was handed over to Kenyan officials in Nairobi.

Foreign Ministry spokesman Altaf stressed without elaborating that the case was a matter between Pakistan and Kenya.

In another development Sunday, the U.S. State Department cited a "very serious threat" to U.S. facilities and citizens in Pakistan and ordered the evacuation of all non-essential employees at the U.S. Embassy in Islamabad.

American officials have considered bin Laden a prime suspect behind the two African bombings from the very beginning. He has never concealed his hatred for the United States and has been accused of sponsoring previous terrorist acts, including the November 1995 attack in Riyadh, Saudi Arabia, that killed five U.S. servicemen and two Indians.

The Associated Press contributed to this report.