The operation was launched in Ramallah, and the list of detainees contained 1,500 names of senior Hamas members and activists.
Sources in the Gaza Strip said that all Hamas members which were not held by Israel were expected to be arrested in the operation, which would only be halted if Hamas declared that it would accept a ceasefire in the coming hours.
The list of detainees contained Hamas mayors, university and charity activists, and people involved in the organization's religious activity.
This was the first wave of detentions launched by the PA against Hamas members since the end of the 1990s. PA officials said the operation reminded them of the wave of detentions carried out after Hamas' series of terror attacks in Israel in 1996, when the PA's prisons were filled with hundreds of senior Hamas members.
Aides to Palestinian President Mahmoud Abbas said that the decision on the operation was made after Hamas did not hide its plan "to destroy any remnant of the Palestinian Authority in the Gaza Strip," and after his efforts to convince Hamas members to reach a ceasefire failed.
Abbas is also expected to declare the disbandment of the Palestinian government and the Palestinian Legislative Council in the coming hours, and declare a state of emergency in the PA and different steps he plans to take against Hamas.
His associates said that he had briefed a number of international Arab officials on the details of his plan and that he had been in touch with Hamas politburo chief Khaled Mashaal in the past few days.
On Wednesday, Abbas spoke to Palestinian Prime Minister Ismail Haniyeh, but all his efforts for a ceasefire failed, and therefore he decided to take a number of harsh retaliation acts against Hamas.
Hamas rejected any offer for a dialogue with the "betraying faction" in Fatah. A senior group member said that a dialogue with elements representing the Israeli interests was impossible.
"This is a battle between Islam and the heretics. We hope to complete our takeover of the PA headquarters by the morning. I hope we can hold the Friday prayers at the Gaza headquarters compound, and we will turn the Sariya compound into a large mosque," said Nizar Rian, a Hamas leader in the Strip.
Dahlan to prepare security organizations
The PA security organizations completed the lists of Hamas detainees on Wednesday night. A Palestinian source told Ynet that the decision on the detentions was made after it became clear that in spite of the Hamas attack in the Strip, Palestinian security organizations managed to hold on mainly in the last power centers in Gaza, which Hamas was having difficulties to take over.
Meanwhile, Palestinian sources in the Strip reported that Mohammed Dahlan, Abbas' national security advisor, secretly arrived at the Palestinian security organizations' compound in Gaza.
According to the report, Dahlan is expected to prepare Fatah forces to launch a counterattack against Hamas' plan to take over the last two headquarters. The report has yet to be confirmed by aides to Dahlan, who recently left the Strip for a series of medical treatments in Germany.
At least 30 Palestinians were killed Wednesday in battles between Hamas and Fatah members in the Gaza Strip. Hamas members took over most of Fatah's posts in the Strip, excluding the Ansar compound and another building belonging to the Palestinian Preventive Security Service.
The violent clashes spread to the West Bank, as Fatah members in Jenin took over a Hamas school and hospital, as well as a number of the movement's offices in the city.
Zakaria Zubeidi, the al-Aqsa Martyrs' Brigades leader in the city, told Ynet that Fatah decided to ban any Hamas activity in the city until the clashes in the Gaza Strip were halted.