© AP Italian activist Vittorio Utmpio Arrigoni holds his passport during a protest against the Israeli siege on Gaza, in Gaza City, in this August 29, 2008 file photo.
Two suspects have reportedly been arrested in the alleged kidnapping and subsequent murder of Vittorio Arrigoni, an activist in the International Solidarity Movement; Arrigoni was hanged in an Islamist militant's home.

The body of an Italian pro-Palestinian activist was found hanging in the home of a Palestinian militant in the Gaza Strip early Friday, hours after he was reportedly kidnapped.

Hamas officials reported that the body of Vittorio Arrigoni, 36, was discovered in the home of a member of the Monotheism and Holy War group that claimed responsibility for the abduction in a video released Thursday.

Two suspects have already been arrested, and Hamas claims to be searching a third.

The video claiming to show the victim emerged from Gaza on Thursday afternoon, teamed with the extremist group's demand that Hamas release its leader who was arrested last month. The group threatened to execute the hostage if it demands were not met by Friday afternoon.

Co-founder of the International Solidarity Movement, Huwaida Arraf, confirmed that the abducted man in the video appeared to be one of its activists, identifying him as Arrigoni.

Later Thursday, Hamas police reportedly stormed a Gaza City apartment and found Arrigoni's body. In a statement, the Hamas Interior Ministry said the man was killed "in an awful way" shortly after he was abducted at mid-day Thursday.

Interior Ministry spokesman Ehab al-Ghussein said the kidnappers had planned from the beginning to kill their victim not to trade him for captives. He also said that a member of the militant group led them to the house.

The Palestinian People Party, a faction of the Palestine Liberation Organization that is headed by Palestinian President Mahmoud Abbas, condemned the killing and demanded the killers face the "utmost punishment."

"This crime does not reflect the morals or the traditions of the Palestinian people," the group said in a statement.

An Italian doctor was reportedly on his way to Gaza from Israel to identify Arrigoni's body.

The video released by the militant group shows a man with a thick black blindfold and a large bruise on his face. Apparently seated, he is held in front of the camera by an unseen person.

In a message on the video, the extremist group demanded that Hamas free its leader, arrested in early March, and two other members whose names had not been previously known.

Sheikh Abu Walid-al-Maqdasi, the leader of the group, was arrested in a crowded beachside neighborhood of Gaza City last month.

Although Hamas authorities were responsible for locating Arrigoni, Hamas itself is a fundamentalist Islamic group. But it faces challenges from even more extremist offshoots of Islam, including Walid-al-Maqdasi's group, that take inspiration from Al-Qaida and the world jihad movement. Hamas has denied that al-Qaida has a presence in Gaza.

Kidnappings of foreigners were common before the Hamas takeover. Most of those abducted were foreign correspondents, including Alan Johnston of the BBC, who was abducted and held for 114 days before being freed in July 2007, just after Hamas overran Gaza, expelling forces loyal to Palestinian President Mahmoud Abbas.

ISM, the organization to which Arrigoni belonged, operates in the West Bank and Gaza and is known for trying to prevent the Israeli military from carrying out its missions. Arraf said this activist has been going in and out of Gaza for more than two years. He was working with farmers and fishermen.

The ISM incident that got the most attention was the 2003 death of American activist Rachel Corrie, who was crushed by an Israeli military bulldozer in southern Gaza while trying to block its path.