A shootout at a mosque in the southern Gaza city of Rafah between Hamas security men and a more extreme Islamist group called the Warriors of God ended early Saturday with 22 dead, including the group’s leader and a senior Hamas security officer.

The Ministry of Interior in Gaza said the leader, Abdel Latif Moussa, died in an explosion at his house near the mosque when fighting resumed after dawn. A ministry spokesman said his death might have resulted from explosives in his house that detonated when security men sought to reach him.

Hospital officials in Rafah said the dead included an 11-year-old girl and six Hamas policemen. About 150 people were wounded. By noon on Saturday, Rafah was calm after hours of gun battles.

The Warriors of God, which is based there, had taken over the mosque with about 100 men. Mr. Moussa had asserted during Friday Prayer that Hamas was lax in its observance of Islamic law. He announced that the city — and soon all of Gaza — was coming under strict religious law.

Hamas, an Islamist but also Palestinian nationalist movement that took over Gaza two years ago, faces rebellion by some splinter groups accusing it of being too liberal. The Warriors of God referred in its literature to taking inspiration from and having links to Al Qaeda, though it is not clear whether those links are real. What is clear is that it wants Gaza to be more aggressively Islamist and to be part of a worldwide jihad, rather than engaged in a fight for a Muslim Palestinian state.

Hamas makes a point of saying it does not impose strict Islam on others but merely sets an example. There are, nonetheless, Palestinians in Gaza who are more moderate religiously and who oppose Hamas, complaining of creeping theocracy in its rules and laws.