Hamas Islamists ruling the Gaza Strip face a growing security challenge from al Qaeda-inspired Palestinian groups in the religiously conservative enclave.

Fundamentalist Muslims, or Salafis, whose agenda of global jihad, or holy war, against the West is against Hamas's nationalist goals, have stepped up bombing attacks in the Gaza Strip in recent weeks, targeting Hamas security men and offices.

Analysts say those groups, which identify with al Qaeda but have no clear hierarchical connection to it, do not pose an immediate threat to Hamas's rule over the Gaza Strip, but will remain a thorn in the movement's side in the foreseeable future.

"Hamas is capable of besieging and weakening them but that would be costly on political, security and moral levels because the conflict would be among groups that hold the same religious ideology," said political analyst Talal Okal.

He described the radical Islamist groups as a security concern for Hamas, a movement the Salafis believe broke with Islam by taking part in a U.S.-backed 2006 Palestinian election, a vote it won.

A year later, Hamas seized control of the Gaza Strip from Palestinian President Mahmoud Abbas's secular Fatah party.

Both groups have failed to seal a unity deal despite lengthy Egyptian mediation. Okal said Hamas-Fatah reconciliation could help to weaken the Salafis by strengthening democratic values and pluralism in the Gaza Strip.

STRONG MESSAGE

Sources close to Salafi groups said fundamentalists set off three bombs in the Beach refugee camp last week near the heavily guarded home of Hamas prime minister Ismail Haniyeh.

The sources described the blasts -- a departure from previous attacks that targeted Internet cafes and Christian churches -- as a message to Haniyeh to order a stop to an arrest campaign against their members. No one was hurt.

Salafi groups in Gaza range in strength from Jund Ansar Allah (Warriors of God) and Jaysh al-Islam (Army of Islam), both believed to have several hundred members, to smaller groups with a few dozen people in their ranks.

Some are former allies of Hamas, or include former members of the Islamist group who later turned against it.

Ehab al-Ghsain, spokesman for the Hamas-run Interior Ministry, played down the attacks, saying the bombs were home-made stun grenades and that security forces detained a man who made them. He said the suspect had no factional connections.

Salafi sources said the people who placed the bombs were sympathisers among Haniyeh's guards in his compound.

In fresh violence, unknown assailants detonated a bomb on Monday underneath the car of a top Hamas police officer in Gaza, a Palestinian human rights organisation said. No one was hurt and there was no immediate claim of responsibility.

In January, a bomb destroyed a senior security official's jeep in Gaza. There were no casualties. Last month, a senior Hamas commander in the southern Gaza town of Rafah escaped injury in a bomb blast. Sources close to Salafi factions said the two officers were involved in "killing and torturing" Islamist fighters.

In the most serious violence between Hamas and the Salafis, Hamas forces attacked a mosque in Rafah last August after the leader of a group calling itself Jund Ansar Allah declared Islamic rule in the town on the border with Egypt.

Up to 28 people, including the leader, were killed.

Since then, Salafi groups have accused Hamas of trying to block them from firing rockets into Israel, which carried out a punishing Gaza offensive last year in a declared bid to curtail such cross-border attacks.

"If (Hamas) implemented Islamic law and the rule of God then we would be its soldiers, until then we see it as a secular government that obstructed the rule of God," said a Salafi member who identified himself only as Abu Abdallah.

Using tougher rhetoric against Hamas, other members of the Salafi groups told Reuters they considered Hamas legislators to be apostates, but they had no orders to act against them.

"So far our orders have been to spread the word of God and to fight only the Jews. Should our sheikhs (clerics) order us to target those who hurt us, we will hurt them badly," said Abu Abdallah.

Abu Abdallah and another Salafi member said Salafi groups avoided forming their own unified coalition in order to make it harder for Hamas to target them, but maintained direct contacts and coordinated their moves.

They have no factional ties with al Qaeda but consult with and follow instructions from well-known al Qaeda advocates like Jordan's Abu Mohammad al-Maqdisi, a former mentor of Abu Musab Al-Zarqawi, a Qaeda commander killed by U.S. forces in Iraq in 2006.

Salafi activists voice their respect and loyalty to Qaeda chief Osama Bin Laden and his second in command Ayman Al-Zawahri.