Hamas, the Islamist movement which rules Gaza, said on Saturday it will take legal action against members of the rival Fatah faction who defy a ban on leaving the Palestinian enclave to attend a major party congress.
Fatah members who travel to the West Bank town of Bethlehem for Tuesday's congress will be prosecuted on their return to the Gaza Strip, the Hamas justice ministry said in a statement.
According to sources close to Fatah, around 12 delegates from Gaza have managed to evade tight Hamas security checks to enter Israel and travel to the West Bank through the Erez crossing.
But several others have had their identity papers confiscated to ensure they cannot leave the territory.
Mahmud Zahar, a senior Hamas leader in Gaza, said earlier this week the ban on participating in the congress would be lifted if Fatah freed all Hamas prisoners in the occupied West Bank.
The ban affects the more than 400 Fatah members who currently live in Gaza and are eligible to attend the congress, officials said.
The congress will be Fatah's first such meeting in 20 years, with some 2,000 delegates expected to attend from around the world.
Fatah delegates living in Syria and Lebanon will be allowed to attend, an Israeli official said on Wednesday after talks in Jerusalem between Prime Minister Benjamin Netanyahu and US National Security Advisor James Jones.
Hamas-Fatah tensions boiled over in June 2007 when the Islamists seized control of Gaza after a week of deadly street clashes, confining the writ of Palestinian president and Fatah leader Mahmud Abbas to the West Bank.
Since then, each group has accused the other of persecuting its rivals in its respective area of control.
Several months of Egyptian-brokered reconciliation talks have failed to produce an agreement, although a seventh round of negotiations is due to begin on August 25 in Cairo.