Palestinian leader Mahmoud Abbas has placed his security forces on high alert after deadly factional violence in the West Bank and the Gaza Strip.
Offices were ransacked and their windows broken
Mr Abbas ordered troops to take control after gunmen loyal to his Fatah group set fire to Hamas offices in Ramallah.
Violence flared after earlier clashes in Gaza, where two people were killed.
The Palestinian Authority has been dogged by a power struggle since Hamas won elections in January, ousting Fatah from government.
Senior Palestinian negotiator Saeb Erekat, an ally of Mr Abbas, told the BBC he was worried by the extent of the violence and concerned at the breakdown of law and order.
"I'm so alarmed, I'm so concerned, things are slipping outside of our fingers like sand.
"I think we're exerting maximum efforts, [but] we're not really undermining the underlying difficulties and complexities facing us."
The violence began in Gaza, where shots were fired at the funeral of a Hamas member in the southern town of Rafah.
Two people were killed and 15 hurt when Hamas supporters retaliated by attacking the offices of Fatah-dominated security services in the town.
Hamas followers showed their support in Gaza after the violence
That sparked violent reprisals in the West Bank town of Ramallah, where Mr Abbas has his offices.
Gunmen, many from the Fatah-linked al-Aqsa Martyrs' Brigade, shot out the windows of the Palestinian parliament and stormed the cabinet offices, smashing furniture and computers.
An unoccupied office belonging to Gaza-based Prime Minister Ismail Haniya was among those burnt out.
Hamas MP Khalil Rabei was briefly kidnapped, but later released.
War of words
The escalating violence drew sharp comments from the rival factions.
"Every time they touch one of ours in Gaza, we will get 10 of theirs in the West Bank," one member of the security service was quoted by the Associated Press news agency as saying.
A Hamas spokesman, Sami Abu Zuhri, told the Reuters news agency that the violence was "vandalism" and part of an effort to bring down the Hamas government.
Tensions have worsened between the two sides since Mr Abbas called a referendum on a statehood plan which would implicitly recognise Israel, whose right to exist Hamas rejects.
At least 20 people, mostly militia members, have been killed in clashes between the two factions in the past two months.
Earlier on Monday a Hamas gunman was killed in a clash with security forces loyal to Fatah in Rafah.
The man was shot dead during a funeral for a fellow militant in Rafah. Each side blamed the other for firing first.
In addition to the clash at the funeral in Rafah, eyewitnesses say Hamas gunmen fired rocket-propelled grenades and anti-tank rockets at the security headquarters. One person was killed and more than a dozen wounded.