The officers parked their motorcycles and patrol cars outside parliament, government buildings and the offices of the governing center-right New Democracy party and its Socialist coalition partner. The noisy start-and-stop protest lasted more than five hours.
It launched a week of planned demonstrations against the latest round of austerity measures that will impose staff cuts on teachers and local government. Municipal authorities across Greece including the Athens municipal police, who are generally tasked with checking parking violations and checking street vendors have suspended services for three days, while unions have called a general strike for Tuesday.
The strike is set to disrupt flights, national rail travel and public hospitals.
Greece's international creditors demanded the job cuts before approving new bailout loan installments worth 6.8 billion euros ($8.9 billion) from a massive rescue fund worth 240 billion euros ($312 billion). The latest batch of loans will be paid out between July and October.
Public sector workers, while slapped with repeated salary and benefit cuts, have been spared firings until this year.
The measures are to be voted on by parliament this week the first major political test for Conservative Prime Minister Antonis Samaras since a left-wing party abandoned his coalition government last month, leaving it with a reduced majority.
Samaras' 13-month-old coalition has promised to fire 15,000 public sector employees by the end of 2014 and transfer another 12,500 to new positions this year, most following an eight-month suspension on reduced pay.
He is facing renewed opposition from the left-wing Syriza party, which has made a campaign promise to re-hire dismissed public servants and at the weekend voted to overhaul its party structure to prepare for potential early elections.
Government officials met with protesting mayors Monday and insisted there was room for changes in the new austerity bill to be voted late Wednesday, but they ruled out backing the major amendments demanded by local government.
"We are not opposed to reform ... What we do oppose is abolishing entire institutions like the municipal police and personnel to guard state schools," said Costas Askounis, leader of the protesting Central Union of Municipalities.
Greece has been kept out of bankruptcy since it started receiving rescue loans in 2010 from other euro countries at the International Monetary Fund, but austerity measures demanded in return have caused a dramatic increase in poverty and unemployment.
German Finance Minister Wolfgang Schaeuble, considered an architect of bailout austerity measures in the eurozone, is due to visit Athens on Thursday.
Shares on the Athens Stock Exchange fell 0.5 percent on Monday, while markets elsewhere in Europe rose slightly.