Riots once more erupted outside the Greek parliament in central Athens Tuesday as riot police used tear gas on rock throwing demonstrators protesting against more taxes and spending cuts.

The police tried to keep crowds away from lawmakers, as the debate continued over the government's austerity proposals essential for the country to receive critical bailout funds that will prevent a potentially disastrous default.

At the same time, a general strike called by unions furious with the government's new $39-billion Cdn program of taxes on minimum wage earners and other measures to bring the government budget under control disrupted services across Greece.

Tens of thousands of angry protesters turned Athens into a violent riot scene. Demonstrators ripped up paving stones and set trash bins on fire.

Police said 37 officers were injured, while 14 protesters were arrested. Emergency services said nine protesters were injured.

Young men set fire to a TV satellite truck parked near parliament. The vehicle rolled downhill into a kiosk where a freezer exploded. Hooded youths ducked behind the burning truck to help themselves to ice-cream cones.

The latest measures must pass in two parliamentary votes Wednesday and Thursday if Greece is to receive bailout funds from the EU and the IMF that will keep it from becoming the first euro zone nation to default on its debts.

CBC News reporter Susan Ormiston reported that dozens of people have been going at the police back and forth.

"They've been throwing firebombs at the police. The police have responded with tear gas," she said.

The day began with about 20,000 people marching peacefully in two separate demonstrations, with another 7,000 protesting in the northern city of Thessaloniki without incident.

"The situation that the workers are undergoing is tragic and we are near poverty levels," said Spyros Linardopoulos, a protester with the PAME union blockading the port of Piraeus. "The government has declared war and to this war we will answer back with war."

Staff at upscale hotels handed out surgical masks to tourists and helped them with rolling luggage past the rioting, over ground strewn with smashed-up marble and cement paving stones.

Protesters throw stones to riot police during a demonstration in Athens on Tuesday. Petros Giannakouris/Associated Press

"The troublemakers are attacking the police fiercely and trying to disrupt a peaceful protest," police spokesman Athanasios Kokalakis said. An ongoing strike by electricity company workers kept up rolling blackouts across Greece.

Not far from the violent protest, cafés and ice cream vendors popular with tourists used portable generators to keep the power on.

Hundreds of flights were cancelled or rescheduled as air traffic controllers walked off the job for four hours in the morning.

Strikes by public transport workers snarled traffic across the capital and left tourists stranded around Piraeus.

Strike started out peacefully

The tone started out as a peaceful strike across all divisions of the country's massive public sector.

Everyone from doctors and ambulance drivers to casino workers and even actors at a state-funded theatre were joining the two-day strike or holding work stoppages for several hours.

But as the hours wore on, pockets of violence erupted. Lines of riot police clashed with crowds of young men, with the two sides hurling tear gas canisters at each other.

Hundreds of flights were cancelled or rescheduled as air traffic controllers walked off the job for four hours from 8 a.m. Another walkout is expected in the evening.

The package and implementation law must be passed in parliamentary votes this week so the European Union and the International Monetary Fund can release the next installment of Greece's $155 billion bailout loan.

A demonstrator smashes windows in Athens. Thanassis Stavrakis/Associated Press

Without it, Greece faces the prospect next month of becoming the first euro zone country to default on its debts — a potentially disastrous event that could drag down European banks and affect other financially troubled European countries.

A three-day debate on the new austerity measures got under way in parliament Monday, with Socialist Prime Minister George Papandreou buoyed by word that French banks are willing to defer Greek debt claims and ease pressure on Athens.

"I call on you to vote for survival, growth, justice, and a future for the citizens of this country," Papandreou told legislators.

After a year of cuts, Greece's financial situation is no better, which has caused Greeks to question the need for more austerity.

"The Greeks are not convinced that further cuts to their standard of living is going to fix the problem," Ormiston said.

With files from Susan Ormiston and The Associated Press