GAZA CITY, Gaza Strip ? A new security force made up of gunmen from militant groups faced off with police outside a refugee camp. In Gaza City, they marched with black T-shirts and black woolen masks, toting submachine guns and grenade launchers, almost daring the veteran police to react.

It was street theater, a least for a while Wednesday. The new force of 3,000 militants, headed by a notorious gunman, represented the most brazen affront yet by the Hamas-led government to moderate President Mahmoud Abbas, coming close to violent confrontation but not crossing the line.

The sudden show of force came hours after two Hamas members were gunned down in mysterious drive-by shootings that the group blamed on Abbas’ Fatah Party.

The deployment defied a presidential order and added to tensions that have been rising since Hamas defeated Fatah in legislative elections in January. The power struggle already has spilled over into violence, and the Palestinian territories increasingly appear headed toward a bloody showdown.