GAZA, April 19 (Nidal al-Mughrabi/Reuters) - Hamas security forces in Gaza stormed a building where killers of a pro-Palestinian Italian activist were hiding on Tuesday and two of the al Qaeda-inspired militants died in the raid, Hamas said.

The Hamas-run government said one of the dead militants, a Jordanian, shot himself after throwing a grenade that killed the second as the security forces burst into the building in the central Gaza Strip where the fugitives had been hiding.

Another of the main suspects in his killing was captured alive, together with three group members who were in the building at the time but had not been identified as culprits.

This is a tough lesson to whomever would think of messing with the security of the homeland and the citizens, Ehab Al-Ghsain, a Hamas Interior Ministry spokesman, told a news conference.

Three members of the Hamas security forces were wounded in the battle to capture the susected killers of Vittorio Arrigoni, members of a jihadist Salafist group which abducted the Italian to press their demand for Hamas to release their jailed leader.

Arrigoni, 36, was kidnapped on Thursday and found strangled on Friday.

Hamas security forces surrounded the four-storey building in the Nuseirat refugee camp early on Tuesday, cordoned off the area and traded gunfire with the militants holed up inside. An attempt to negotiate their surrender failed.

Hisham Al-Seedni, their jailed leader, was brought to the building in an effort to persuade the men not to fight, but his followers ignored him, Ghsain said.

The Hamas security forces also brought the mother of one of the fugitives to persuade them to turn themselves in, Ghsain added, screening footage of the woman pleading with her son outside the building.

At least four explosions and heavy gunfire were heard by witnesses as the Hamas security forces stormed the building.
              

SALAFISTS

The militants were jihadist Salafists who espouse a more radical form of political Islam than Hamas and appear to be attracting recruits, including some from Hamas's ranks.

Arrigoni's killing posed an unprecedented challenge to Hamas, which has governed Gaza since it seized control of the coastal territory from forces loyal to U.S.-backed Palestinian President Mahmoud Abbas in 2007.

Vittorio's killing was meant to show Hamas was not in full control of the security situation and therefore the speed of action against the group was meant to show that they are still in control, said Hani Habib, a political analyst.

Hamas was enthusiastic about catching or killing this group and they did not spare any effort to do so, he said. Hamas forces were already holding two suspects in his killing.

Arrigoni's death caused outrage among ordinary Palestinians in Gaza. He was known for helping local fishermen and farmers.

He had lived in Gaza since arriving in 2008 aboard a humanitarian aid boat that Israel had permitted to dock, despite imposing a blockade on the territory after ending its occupation of Gaza in 2005.

Hundreds of Palestinians took part in a symbolic funeral for Arrigoni on Monday.

The Hamas government, which is deeply hostile to Israel, had denounced the kidnapping and killing as an attempt to harm international solidarity with Gaza.

Arrigoni was the first foreigner to be abducted in Gaza since BBC journalist Alan Johnston, who was held for 114 days by another al Qaeda-inspired group. He was released in 2007.

Salafist groups have accused Hamas, an offshoot of the Muslim Brotherhood, of being insufficiently committed to enforcing their vision of Islamic law. They have attacked Internet cafes and other targets and want Christians expelled.

They also condemn Hamas for considering ceasefires with Israel and exploring political accommodation with secular Palestinian rivals.

(Writing by Tom Perry, editing by Tim Pearce)