Hamas said Thursday it has arrested the assassin behind the hit on a top Hamas militant, Mazen Fuqaha, in March.

"Everyone knows Israel wanted to severely damage Hamas and the resistance, and to undercut morale and strategy, so it was important that we solve the assassination," the group's leader, Ismail Haniyeh, said in a Gaza press conference. "Therefore, the security forces in the Strip moved on all fronts to reach the moment in which the murder was solved."

Open gallery view Fuqaha, right, with Ahmed Jabari, a leader of Hamas' military wing who was killed in an IDF strike in 2012. Credit: Twitter

He stated: "We've arrested the assassin who pulled the trigger. The murderer was following the instructions of his Israeli commanders, and confessed to the act, and shared all the details with his investigators."

Haniyeh said that the assassin "will be executed according to the principle of justice of the people fighting the occupation." He noted that the Palestinian interior ministry would hold a press conference in the coming days to provide details of the assassination.

"The solving of the crime has strategic repercussions and great importance, and the world will yet be surprised by the strength of the Palestinian security services in Gaza," boasted Haniyeh. He asserted that the announcement of the arrest had been postponed a few days "in order to clarify all the details."

He also said, "There is no doubt that great harm was done to the organization, but a quick resolution was the answer."

Senior Hamas official Ismail Radwan, who also participated in the press conference called by Haniyeh, said, "The resistance forces will respond to the assassination of Fuqaha, and his blood and the blood of the rest of the Palestinian martyrs will not be abandoned."

Fuqaha, a senior member of Hamas’ military wing, was gunned down on March 24 in the southern Gaza City neighborhood of Tel al-Hawa, according to the Gaza foreign ministry. The gunmen were equipped with silencers, the ministry's statement said at the time. A police spokesman in Gaza said the assailants had shot Fuqaha four times in the head.

Israel sentenced Fuqaha to life in prison and an additional 50 years for planning a suicide bombing on a bus in northern Israel in 2002, which killed nine Israelis. But in 2011, Fuqaha was released as part of a prisoner exchange deal to free Israeli soldier Gilad Shalit.

Fuqaha, originally from the village of Tubas in the northern West Bank, was exiled at Israel’s demand to Gaza. He was considered a senior member of Hamas’ West Bank command, which gave orders and funds to West bank cells.

Israel's Defense Minister Avigdor Lieberman told the Yedioth Ahronoth newspaper after the incident that Fuqaha's death was an inside job within the movement.

Internal assassinations are characteristic of terror groups, Lieberman said. “We can say with certainty that it was an internal killing,” the minister said. “I wouldn’t be surprised if during the Iranian election on May 19, somebody assassinates the president of Iran, Hassan Rohani.”

Until now, Lieberman has been muffled on the subject of Fuqaha’s assassination, which Hamas has blamed on Israel, claiming that the “fingerprints are clearly Mossad’s." Israel has ignored the accusations against it.

Hamas has threatened to take revenge. A video posted online last month by a news site linked to the terrorist group in Gaza showed a camouflaged sniper peering through a scope at prominent Israeli officials, including Lieberman, followed by the message in Hebrew and Arabic, "We will act in kind."