The three men accused of assassinating a senior Hamas commander in March have confessed to the crime and admitted that they received instructions from Israel for carrying out the killing, according to Gaza officials.

Mazen Faqha, of Hamas's military wing, was fatally shot in the head and chest at the entrance of his Gaza City home on March 24.

"The three collaborators confessed that they received instructions to surveil Faqha and his home," Major General Tawfiq Abu Naim, commander of internal security forces, said in a news conference on Tuesday.

A "large security operation" resulted in the arrest of "a network of 45 Palestinian collaborators" within the Gaza Strip, he added.

"The assassination was carried out by Israeli intelligence officers who were communicating [with the collaborators] through telephones and communications equipment."

The announcement came five days after Hamas said it had arrested Faqha's killer, adding that the suspect had carried out the assassination on Israel's orders. Ismail Haniya, the newly-elected leader of Hamas's political wing, said on May 11 that more details would be released soon.

A video released on Tuesday showed the steps, including Faqha's surveillance, carried out to assassinate Faqha according to the confessions obtained by Hamas.

Hamas says the video proves Israel's role behind the operation.

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Israel's defence ministry has denied involvement in the assassination, Al Jazeera's Harry Fawcett, reporting from Ramallah, said.

"However, this was a man [Faqha] on the top five of Israel's most wanted," Fawcett added.

Israel has a history of carrying out extrajudicial assassinations of Palestinian leaders, both political and military, including the killing of Hamas leader Ahmed Yassin in Gaza in 2004.

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Faqha was a senior Hamas official in the Israeli-occupied West Bank when he was jailed by Israel in 2003 for planning attacks against Israelis.

He was sentenced to nine life terms but was released into the Gaza Strip as one of more than 1,000 Palestinian prisoners that Israel let go in exchange for soldier Gilad Shalit.

Hamas has governed the Gaza Strip since 2007.

The small strip of land, home to nearly two million Palestinians, has been under a crippling Israeli blockade for a decade, while Egypt's crossing with the enclave has remained largely closed in those years as well.