Hamas has recalled about 7,000 members of its security forces to reassert control over areas of Gaza recently vacated by Israeli troops, according to local sources.
The Palestinian group also appointed five new governors all with military backgrounds, some of whom previously commanded brigades in its armed wing.
The mobilisation order was reportedly issued via phone calls and text messages which said the aim was to "cleanse Gaza of outlaws and collaborators with Israel" and told fighters to report within 24 hours.
Reports from Gaza suggest that armed Hamas units have already deployed across several districts, some wearing civilian clothes and others in the blue uniforms of the Gaza police.
Tensions rose sharply and quickly after two members of Hamas's elite forces were shot dead by gunmen from the powerful Dughmush clan in Gaza City's Sabra neighbourhood. One of them was the son of a senior commander in Hamas's armed wing, Imad Aqel, who now heads the group's military intelligence.
