The fighting again threatens the fragile Palestinian unity government, and has fuelled fears of all out civil war.
 
The political leaderships of both sides called a truce for 1700 GMT, although previous ceasefires have lasted just hours.
 
Factional fighting has killed at least 40 Palestinians since Friday.
 
'No red lines'
 
The streets of Gaza City echoed with the rattle of gunfire, as witnesses said fighters battled in civilian areas using rocket propelled grenades and machine guns.
 
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"There are no red lines. There is no consideration for the safety of anybody," said Odeh.
 
Terrified residents huddled in dark homes after electricity to some downtown neighborhoods was cut off by a fallen power line.
 
In one panicked call to a radio station, a woman appealed to Palestinian leaders to act, pleading: "Do not leave us to die here."
 
Escalating violence
 
Hamas fighters stormed the home of Abbas's top security chief, Rashid Abu Shbak, in Gaza City early in the morning, killing five guards.
 
Journalists were trapped in Al Jazeera's
Gaza bureau by the fighting
In Wednesday's deadliest single attack, five detained Hamas fighters and two Fatah escorts were killed when their vehicle, travelling to a detention centre, came under fire.
 
Security officials said the vehicle was attacked by Hamas fighters, but a spokesman for Hamas's Executive Force said they were "executed ... in cold blood" by Fatah.
   
Hamas said another of its members was "executed" earlier in the day by Fatah gunmen at a checkpoint.
 
Fatah said at least nine of its members were killed in Wednesday's fighting, including four guards at Abu Shbak's home, a member of Mahmoud Abbas's Presidential Guard and two members of Preventive Security.
 
Fatah's forces are larger in number. But many analysts believe Hamas's Executive Force and armed wing are better equipped and organised.
 
Israeli attacks
 
An Israeli aircraft carried out airstrikes on Gaza on Wednesday.
 
At least four Palestinians were killed in an attack on a Hamas position near the border with Egypt.
 
One Palestinian was also killed and four wounded in an air attack on the northern Gaza Strip on Wednesday.
 
The attack came after Hamas fighters earlier fired rockets at the Israeli town of Sderot, injuring three people.
 
Ehud Olmert, the Israeli prime minister ordered a "severe response" the rocket fire, according to a statement from his office.