The masked gunmen threw themselves to the ground, rolled over and came up firing their assault rifles at an imaginary target.

Jaysh al-Ummah, or the Army of the Nation, a Palestinian Islamist group modelled on the ideology of Osama bin Laden's al Qaeda, was training for battle with Israel.

"We are coming, Jews," read graffiti daubed on a wall inside its private training base in the Gaza Strip, where Reuters journalists were allowed rare access.

"Run, run, take the ground, shoot," Abu Hafss, Jaysh al-Ummah's leader, cried as some 25 gunmen, all clad in black, performed drills.

Jaysh al-Ummah refuses to say how many members it has in the Gaza Strip, territory seized by Hamas Islamists from the largely secular Fatah faction in June 2007.

Hamas allows it to operate, with the unwritten understanding that it stays out of internal Palestinian politics and does not use force to implement its beliefs on the people of Gaza.

The 35-year-old Abu Hafss, who has been briefly detained several times by Hamas, said Jaysh al-Ummah is not part of al Qaeda but "we share the same religion with our brothers and follow the path of our dear Prophet".

Pro-al Qaeda groups raised their profiles in the Gaza Strip after the Hamas takeover. Abu Hafss said al Qaeda's fundamentalist Islamic ideology was flourishing in the territory.

As part of that philosophy, Abu Hafss said, Muslims all over the world were obliged to fight the Israelis and the "infidels" until only Islam rules the earth.

Abu Hafss said his group relied on donations from residents of the Gaza Strip to finance its activities, which have included participation in fighting against Israeli soldiers carrying out raids against militants in the territory.

"The sons of Zion are occupiers and they must be uprooted completely," he said, ruling out any negotiations with Israel. "We will fight them as we are ordered by God and the Prophet Mohammad."

Hamas, whose charter calls for the destruction of the Jewish state but whose leaders agreed to a ceasefire with Israel in June, has said it does not support the actions and statements of al Qaeda.

"We say that the world will not live in peace as long as the blood of Muslims continues to be shed," Abu Hafss said.