Hamas arrests Fatah members in Gaza ahead of rally
Hamas denied the accusation, with a spokesman for the enclave's interior ministry saying 38 people had been held for questioning over concerns that opposing Fatah factions in Gaza would clash at the rally set for later in the day.
All had been released, said spokesman Iyad al-Bozum.
Fatah and Hamas remain deeply divided and Abbas, based in the occupied West Bank, has sought to increase pressure on the Islamist movement in recent days.
"More than 500 of our members and sons have been arrested since last night by Hamas security forces in Gaza," Atef Abu Saif, a spokesman for Fatah in the Gaza Strip, said in a statement.
Saif said the arrests were an attempt by Hamas to disrupt activities to mark Fatah's 54th anniversary.
But there were also concerns over tensions between Fatah factions loyal to Abbas and his exiled rival Mohammed Dahlan, who is from Gaza and has a significant base of support there.
Repeated attempts to reconcile Fatah and Hamas have failed. A list of issues have kept them apart, including Hamas's refusal to disarm its military wing.
Abbas moved earlier this month to dissolve the Hamas-controlled Palestinian parliament, which has not met since 2007, when the Islamist seized control of the Gaza Strip.
While the parliament has been largely defunct, Palestinian law allows for its speaker to act as interim president should 83-year-old Abbas die in office.
Abbas' move came after the Palestinian Constitutional Court in Ramallah issued a ruling to dissolve the parliament and hold elections within six months.
It also comes after Palestinian security forces on Wednesday prevented a press conference by the speaker of the Hamas-controlled Palestinian parliament after the court order.
A spokesman for the Palestinian security services said they were enforcing the court decision and that former members of parliament no longer have the right to use the building since the body has been dissolved.
In comments to Hamas' al-Aqsa television, Hamas member Aziz Dweik said he had been detained at a checkpoint and denounced the actions of the security forces, calling the court's decision illegal.
Hamas has said it rejects the move by a court created by Abbas "to legitimise his arbitrary decisions".
Hamas won the last parliamentary elections in 2006 in a landslide, resulting in an electoral dispute with Fatah.
The Islamists seized control of the Gaza Strip the following year, and the split between them and Abbas' Fatah has persisted.
Abbas has sought to pressure Hamas through other measures, including reducing salaries in Gaza, which is under an Israeli blockade.
Abbas' term was meant to expire in 2009, but he has remained in office in the absence of elections.
Agencies contributed to this report.
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