The Palestinian Authority has condemned Israel's arrest of Hamas politician Aziz Dweik, speaker of the Palestinian Legislative Council.
Mr Dweik was detained by soldiers on Thursday at a checkpoint near the West Bank city of Ramallah on suspicion of being a member of a terrorist group.
Palestinian officials said they would mount a campaign for his release.
Hamas said the arrest was intended to undermine its recent attempts at reconciliation with the Fatah movement.
The deputy speaker of the PLC, Ahmed Bahr of Hamas, said President Mahmoud Abbas - who is also leader of Fatah - should suspend the exploratory peace talks with Israel which took place in neighbouring Jordan this month. Both sides said there was no breakthrough.
"What happened requires Mahmoud Abbas to declare an immediate stop to the negotiations in Amman in respect of our people and in respect of the parliament and its head," Mr Bahr told reporters in Gaza City.
"It should be a firm message to the Occupation [Israel] that their continued crimes will not be given cover by the Palestinian Authority and will not pass without a response."
Hamas won the Palestinian parliamentary elections in 2006 and seized control of the Gaza Strip from forces loyal to President Abbas and Fatah a year later, since when the PLC has not functioned formally.
The Israeli government says Hamas is a terrorist organisation, committed to the destruction of the Jewish state. About 20 of the Islamist movement's 74 MPs in PLC are currently being held by the Israeli authorities.
Mr Dweik was arrested by Israel in 2006 and spent almost three years in prison after being convicted of belonging to an illegal organisation.
The BBC's Wyre Davies in Jerusalem says Mr Dweik is an influential figure in Palestinian political circles.
Many will see his arrest as a provocative act, our correspondent adds.
Last year, Fatah and Hamas agreed to form an interim government of technocrats whose task would be to prepare for long-delayed elections.
But in June, a meeting to unveil the new government was called off because of a lack of an agreement on the post of prime minister. Hamas rejected the reappointment of Salam Fayyad, President Abbas's choice.
Israel has expressed disapproval at the reconciliation efforts.