WASHINGTON (Reuters) - Israel has allowed a former U.S. congresswoman, Cynthia McKinney, to return home days after detaining her and other activists on board a ship carrying relief supplies for Gaza, a pro-Palestinian group said on Monday.

Israeli authorities intercepted the vessel, which had 21 activists on board, on June 30 and said it would not be permitted to enter Gaza's coastal waters because of security risks in the area and an existing naval blockade.

McKinney has been released, a statement by the American Muslims for Palestine said.

The statement said another American, John Judge, was still being detained. But later on Monday, a spokeswoman for the group, Kristin Szremski, corrected this to say that Judge was not being held.

"McKinney and the others were taking much needed food and medical supplies to the 1.5 million residents of Gaza, where Israel's two-year blockade has resulted in a complete economic breakdown that has forced more than 70 percent of the population into abject poverty," said the statement from the group based in Palos Hills, Illinois.

Last week a United Nations human rights investigator, Richard Falk, called Israel's seizure of the ship "unlawful."

Israel's ambassador to the United Nations in Geneva, Aharon Leshno-Yaar, rejected that charge and said "clearly the purpose of that ship was to create a buzz and serve as a propaganda vehicle against Israel."

McKinney was defeated for re-election to the U.S. House of Representatives in 2006, not long after she scuffled with a Capitol Police officer at a security checkpoint. She was not charged in that incident but apologized for it.