Clashes among rival Palestinian factions in the Gaza Strip today caused at least six injuries in some of the heaviest fighting in weeks, security officials said.
The clashes erupted less than 48 hours after Palestinian security forces began deploying in Gaza under a new security plan.
Palestinians had hoped the deployment would help curb growing lawlessness and ease tensions between ruling Hamas Islamists and President Mahmoud Abbas's secular Fatah faction.
Hamas said the fighting began before dawn when members of Mr Abbas's national security forces detained a member of Hamas's armed wing. The man was suspected of being involved in firing on security forces overnight.
Hamas militants responded by storming the facility where the man was being held and freeing him. At least two members of the national security forces were injured, one seriously, in the gun fight.
In other clashes this morning, at least one Hamas member was wounded, along with three others.
Internal fighting decreased after Hamas and Fatah formed a unity government two months ago, but tensions have remained high, and a Western aid embargo on the Palestinian Authority remains in place.
Mr Abbas and Prime Minister Ismail Haniyeh of Hamas had ordered the deployment of the police this week as part of the security plan.