Ashkelon, Israel - Israel will release two foreign activists taken off a Gaza-bound flotilla from detention on Saturday before handing them to immigration authorities ahead of their deportation, the rights group representing them said.

Saif Abu Keshek, a Spanish national of Palestinian origin, and Brazilian Thiago Avila were among dozens of activists aboard a flotilla intercepted by the Israeli navy in international waters off the coast of Greece on April 30.

The pair were seized by Israeli forces and brought to Israel for questioning, while the others were taken to the Greek island of Crete and released.

"Today, the Shabak Israeli intelligence agency informed Adalah's legal team that Global Sumud Flotilla (GSF) activists and leaders Thiago Avila and Saif Abukeshek would be released from Israeli detention today, Saturday," the rights group Adalah said in a statement.

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"They will be handed to Israel's immigration authorities later today and kept in custody pending their deportation," it added.

Adalah said it was closely monitoring developments "to make sure that the release from detention goes ahead, followed by their deportation from Israel in the coming days."

On Tuesday, an Israeli court had extended the pair's detention until Sunday to allow police more time to interrogate them, according to their lawyers.

The lawyers then filed an appeal against their continued detention, but it was rejected by a district court on Wednesday.

Spain, Brazil, and the United Nations had all called for their swift release.

Avila and Abu Keshek "have been held unlawfully by Israel for over a week after being taken into Israeli detention," Adalah said on Saturday.

"Throughout their detention, they were held in total isolation under punitive conditions despite the purely civilian nature of their mission," it added.

Both Avila and Abu Keshek had been on hunger strike while in detention, Adalah said, adding that Abu Keshek had "escalated to refusing water on the evening of May 5."

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Israeli authorities have previously rejected allegations of abuse but have filed no charges against the men.

Adalah previously said authorities had accused the pair of "assisting the enemy during wartime" and "membership in and providing services to a terrorist organization."

Israel says both men were affiliated with the Popular Conference for Palestinians Abroad, a group accused by Washington of "clandestinely acting on behalf of" Palestinian militant group Hamas.

The flotilla had set sail from France, Spain, and Italy with the aim of breaking Israel's blockade of Gaza and delivering humanitarian aid to the war-ravaged Palestinian territory.

Israel controls all entry points into Gaza, which has been under an Israeli blockade since 2007.