Ammar al-Dweik, director of the central elections commission (CEC), said the decision was made after gunmen burst into two of its branches in the Gaza Strip and the West Bank city of Nablus, in some cases opening fire, but causing no casualties.
"We have told all our employees to close and leave their offices," Mr Dweik said.
The CEC said gunmen had fired shots at the offices, destroyed equipment and verbally and physically assaulted staff members.
It said the suspension would stay in place "until further notice and until it receives assurances that the safety of CEC personnel will be guaranteed" although Mr Dweik added that the commission would meet Tuesday evening to discuss the situation.
The move means candidates who want to register for the January 25 election will be prevented from doing so until further notice. The registration process was due to expire at midnight Wednesday.
Al-Aqsa blamed
Security sources in Gaza said gunmen from the Al-Aqsa Martyrs Brigades, whose followers are loyal to the ruling Fatah faction, had burst into at least four CEC offices in Gaza City, Beit Lahia, Khan Yunis and Rafah.
Another group of Al-Aqsa gunmen burst into CEC offices in Nablus, where they made off with a computer.
Over the past few days, Al-Aqsa gunmen have stepped up a series of raids on offices of the commission.
The unrest is thought to be linked to a growing dispute within Fatah over the composition of its list of candidates for the legislative elections, which has always been subject to heated wrangling.
Palestinian Authority president Mahmud Abbas "strongly condemned the aggression against the CEC offices and its personnel."
Mr Abbas had ordered the security services "to take the necessary measures to arrest the perpetrators and to ensure the security of the CEC's personnel and offices", a statement from his office said.
However, he also urged the CEC to "resume its work to save the elections and ensure the success of the Palestinian democratic process."
Mr Abbas's office announced late Tuesday that the Fatah list would be unveiled on Wednesday.
An Al-Aqsa statement released in Gaza accused Fatah's leadership of selecting unpopular candidates close to the ruling elite, at the expense of those who had been chosen during the partial primaries over the past few weeks.
It called for the legislative election "to be delayed" to enable the party to hold organised primaries.
It also insisted that the Fatah list be headed up by Marwan Barghuti, the jailed leader of the Palestinian uprising.
"Any list which is not led by our brother in arms Marwan Barghuti does not represent Fatah and we will not accept it," the statement said.
Fatah sources said the central committee was likely to elect either Mr Barghuti or prime minister Ahmed Qorei as head of its list.
Bus link postponed
Israel has put off opening a bus link between the Gaza Strip and the West Bank because of the Palestinian Authority's failure to stop militants from firing rockets on the country.
"Israel has no intention of allowing the passage of convoys between the Gaza Strip and the West Bank while the Palestinian Authority does not act to stop the firing of the Qassam (homemade) rockets," said General Dan Halutz who was quoted by parliamentary sources.
Under an agreement in principle reached between the two sides last month brokered by US Secretary of State Condoleezza Rice, the service was to have begun on Thursday.
The announcement comes as no surprise as last week, Israel froze negotiations on the details.
A spokesman for Prime Minister Ariel Sharon said at the time: "There will be no discussions about these convoys as long as the Palestinian Authority fails to respect its commitments to fight against terrorism."
The security cabinet took the decision on December 6, a day after a suicide bomber from the radical Palestinian movement Islamic Jihad killed five Israelis at the entrance to a shopping mall.
Under the deal, Israel should also allow convoys of trucks to travel between Gaza and the West Bank from January 15.