(Corrects title of Khalil al-Hayya in paragraph 5)

By Mohammed Salem

GAZA, July 25 (Reuters) - A bomb exploded next to a car used by the armed wing of Hamas in the Gaza Strip on Friday, killing three gunmen and a girl, the ruling Palestinian Islamist group and medical officials said.

The attack was the third of its kind in a day, making for one of the biggest flare-ups in internal violence since Hamas routed the forces of Palestinian President Mahmoud Abbas's secular Fatah faction to seize control of Gaza a year ago.

Abbas, finding his authority limited to the West Bank, split with Hamas and revived peace efforts with Israel. More recently he has tried to find reconciliation with his Islamist rivals but they have balked at his precondition that they give up Gaza.

The Hamas armed wing issued a statement blaming "members of the fugitive party" -- a derogatory term for Fatah -- for Friday night's blast at a major junction outside Gaza City.

"We have information that some elements are planning to carry out bombings against the interests and leaders of Hamas in order to sow anarchy," said senior Hamas leader Khalil al-Hayya, whose son, himself a gunman, was wounded in the blast.

Nineteen other Palestinians were wounded, medical officials said, many of them passersby on their way to the beach.

Fatah officials in the West Bank could not immediately be reached for comment on the Hamas accusations.

Gaza had been especially calm since an Egyptian-brokered ceasefire between Israel and Hamas took hold last month.

But the truce has stoked some tensions between Palestinian factions as Hamas has sought to prevent other groups from firing cross-border rockets at Israel.

An Israeli military spokeswoman said she had no knowledge of any Israeli involvement in the junction attack.

Earlier on Friday, bomb blasts rocked a cafe and the home of Hamas politician Marwan Abu Rass in Gaza City. A passerby was killed outside the cafe.

Hamas Interior Ministry spokesman Ehab al-Ghsain accused Fatah of being behind the attack on Abu Rass's home, which caused no casualties. Fatah denied involvement. (Reporting by Nidal al-Mughrabi; Writing by Dan Williams; Editing by XX)

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