A member of the Palestinian militant Islamic movement Hamas, Bassam al-Fara, has been killed by gunmen in the southern Gaza Strip.
Fatah supporters have protested angrily about Monday's brutal killing
Mr Fara, who was also a judge, was shot in the town of Khan Younis.
The armed wing of Hamas blamed gunmen linked to its main political rival, Fatah, for the killing. Fatah rejected the accusation.
Inter-faction tensions have increased since the killing of three sons of a pro-Fatah security chief on Monday.
Reports say unidentified gunmen dragged Mr Fara from a taxi outside the courthouse where he worked and shot him at point blank range.
Witnesses said the gunmen had eaten breakfast in a nearby restaurant while waiting for the arrival of the Islamic court judge, who was also the local Hamas military commander.
Fatah spokesman Tawfiq Abu Khoussa rejected Hamas accusations that his group was behind the attack.
"The brothers in Hamas must be accurate and not fire accusations before the investigation," he said.
Fatah activists suggested that the killing was some kind of personal vendetta.
This was the second murder of a Palestinian judge in the same area in the last week.
Relations between the two Palestinian factions are always strained, but the tension has increased significantly following Monday's attack on the car of a senior Fatah security official, says the BBC's Alan Johnston in Gaza.
He was not in the vehicle, but his three sons, aged between six and 10, were and they all died in the gunfire.
Some in Fatah have openly accused Hamas of being behind that attack, but Hamas has denied this.
On Tuesday, supporters on both sides exchanged gunfire in the Gaza Strip, wounding at least four people.
Hamas and Fatah have been engaged in months of fruitless talks to form a unity government to end the international isolation imposed on the Palestinian Authority since Hamas took power.
Palestinian Prime Minister Ismail Haniya, of Hamas, said he was cutting short a month-long international tour in order to address the growing crisis.
"We will protect the national unity of the Palestinian people and we will thwart any attempt to instigate an inter-Palestinian struggle," Mr Haniya said.
Palestinian Authority President Mahmoud Abbas has not publicly announced his plans, but aides say he may call early elections, a move decried by Hamas as a coup.
Hamas - which does not recognise Israel's legitimacy - won Palestinian parliamentary elections in January, triggering a western diplomatic and aid boycott of the PA.