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GAZA, Oct 2 (Reuters) - Three Palestinians were killed on Tuesday when their car exploded outside a Hamas security office in Gaza and the Islamist militant group which runs the territory accused Fatah rivals of trying to plant a bomb near its outpost.

The incident could stoke internal tensions between Hamas and Palestinian President Mahmoud Abbas's Fatah faction nearly four months after the Islamist group seized the coastal territory by force.

Hospital officials said another Palestinian was wounded in the blast in Gaza City.

A Hamas security official said the three Palestinians who died in the blast belonged to Fatah and accused the secular group of attempting to plant a bomb near one of its security post when their vehicle exploded.

The official said at least one of the men was a "senior Fatah militant," though he declined to provide any of their names.

No Fatah officials were immediately available to comment on the charges.

Hamas officials had earlier identified the four men as members of one of Hamas's security forces and said an Israeli warship fired a shell that destroyed the vehicle.

Israel said it was not involved in any attack.

Hamas's account would make it the deadliest incident of internal violence since Hamas took over in June.

Earlier on Tuesday, Israel sent 29 prisoners home to the territory as part of an attempt to bolster Abbas ahead of a U.S.-sponsored conference on Palestinian statehood.

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