Three Palestinians have been killed in clashes in Gaza between armed men and the security forces.
The violence on Friday was sparked by the death of a Palestinian resistance fighter who died in a car-bomb explosion earlier during the day.
Rival Palestinian factions clashed at the funeral of Abu Youssef al-Quqa, killing three people and wounding at least 20 others, hospital officials in Gaza said.
"We have a big mess here," said Dr Bakr Abu-Safira, an emergency room physician. Hospital officials said two of the dead were bystanders.
A boy was wounded in the head by flying debris after the explosion, but his injury is not life threatening.
Ismail Haniya, the Palestinian prime minister, appealed for calm after the killing, and said the Hamas-led government he leads would launch an investigation.
Haniya told Reuters that he asked his interior minister, Saeed Seyam, to conduct an immediate investigation into the death of al-Quqa, a top commander in the Popular Resistance Committees (PRC), an umbrella group of fighters in Gaza often responsible for rocket attacks against Israel.
Al Jazeera's correspondent in Gaza, Hiba Akila, reported that Israeli artillery on Friday shelled uninhabited arable lands in the northeastern part of the Gaza Strip.
Collaboration alleged
Fighters loyal to al-Quqa accused Palestinian security forces of collaborating with Israel in the killing, triggering a series of gunfights in Gaza after the explosion.
Israel denied any involvement in the blast outside a mosque at the start of Friday prayers that killed al-Quqa.
The PRC initially blamed Israel, but later accused Palestinian security forces.
An Israeli army spokeswoman said: "It wasn't us".
Abu Abir, a PRC spokesman, said that armed men loyal to Mohammed Dahlan, the powerful former Preventative Security Service chief in Gaza and a Fatah member in the new Palestinian parliament, were caught spying on al-Quqa's home on Thursday.
Abu Abir promised "an open war" on Dahlan and several other top security commanders.
Palestinian intelligence officials said al-Quka was a known Hamas supporter, and appeared to have been targeted for his loyalties. The officials, fearing for their safety, spoke on condition of anonymity.
Dahlan, who was travelling in the UAE, dismissed the PRC's allegations as "baseless ugly accusations".
When Abu Abir called a news conference to discuss the killing, rival armed men burst on the scene, sparking a shootout. Hospital officials said two boys, ages 15 and 13, were wounded, one seriously.
Funeral violence
Dozens of armed men gathered outside the hospital where al-Quqa's body was taken, crying, screaming and firing into the air. Accompanying the body, hundreds of armed men marched through the streets of Gaza City.
After the funeral, dozens of Fatah-linked armed men blocked the roads leading to Samir Masharawi, another strongman close to Dahlan. A spokesman for the armed men pledged to take "all necessary measures against Abu Abir. He must be punished".
Mahmoud al-Zahar, the Palestinian foreign minister, said of the Gaza explosion: "It means that the Israeli aggression will not stop. It means our resistance should continue."
The Gaza blast came just a day after a Palestinian suicide bomber killed four Israelis in the West Bank.
Hamas pledge
The new Hamas government meanwhile held an emergency meeting on Friday night and pledged to end public displays of weapons in the Gaza Strip.
Yousef Rizka, the information minister, said the government pledged "to remove all arms from the street".
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