The leader of radical Islamist group Jund Ansar Allah is among 24 people killed in a gun battle with Hamas police in Gaza.
Abdul Latif Musa had declared an al Qaeda-style Islamic "emirate" from a mosque on Friday, defying the authority of Hamas, which rules Gaza. In response, Hamas stormed the mosque and beseiged the cleric's house, where followers of his Jund Ansar Allah (Warriors of God) group were thought to be.
The shooting erupted on Friday afternoon following weekly prayers in Rafah, on the Egyptian border, and continued until dawn on Saturday.
Abdul Latif Musa was killed while fighting Hamas forces besieging his house, the interior ministry said. Witnesses reported a number of explosions there, but it was not clear how he died.
Mohammed al-Shamali, the Hamas military chief for southern Gaza, and five policemen were also listed as killed, and 10 police wounded. One child was also killed.
A Hamas spokesman accused Jund Ansar Allah of colluding with elements of the Palestinian Authority security forces driven from Gaza in fierce 2007 fighting that left Hamas in control of the impoverished coastal strip.
Hundreds of police officers and Hamas forces had also stormed Abdul-Latif Moussa's house, where it is thought at least 100 supporters of the al-Qaeda inspired jihadi group were holed up.
At least one Hamas fighter was killed by a grenade fired from the mosque but most of those killed were supporters of the cleric.
Friday's incident was one of the most violent in Gaza since Israel's 22-day offensive over the new year.