Policemen fired rifles into the air and smashed concrete to stop traffic on Thursday in a further sign of growing unrest over delayed salaries.
Most police were from security services loyal to Mahmoud Abbas, the Palestinian president, who in an increasingly bitter confrontation with the Hamas-led government of Ismail Haniya, the prime minister, over forming a unity government.
Palestinians hope a unity government will lead to the lifting of sanctions imposed when Hamas took office in March.
The embargo has prevented the Palestinian Authority from paying full salaries to tens of thousands of civil servants since.
"Our protest is not politically motivated, it is motivated by the hunger and needs of our children," said one policeman. "Haniya or Abbas, we do not care about their problems. We care about our welfare."
Direct aid was suspended over Hamas' refusal to recognise Israel, renounce the armed struggled and accept peace accords with Israel.
Mushir al-Masri, a senior Hamas politician, accused some "political parties" of sponsoring the rallies.
Security officials blocked the
main roads in Gaza City
He blamed officials in Abbas' office for not making good on the president's promise to help make a full salary payment to 165,000 government workers in September.
"There are administrative measures that were supposed to be made by the president's office. They have not been finalised yet," al-Masri said.
Tawfiq Abu Khoussa, spokesman for Abbas' Fatah movement in Gaza and the West Bank, said that Hamas was trying to escape its responsibility for ending the financial crisis.
"The reality on the ground says people need food for their children. They do not care who pays the salaries, the government or the president," he said.
The police protest comes during a month-long strike by many other government workers, such as teachers, over unpaid salaries.