Some 2,500 protesting truck drivers, carrying Greek flags and shouting "shame" and "thieves," marched through Athens on Tuesday and held a vigil outside parliament, on the ninth day of demonstrations against planned labor market reforms.
Late Tuesday riot police used tear gas to disperse a group of protesters who tried to break a police cordon and damaged a sentry post used by the ceremonial guard at the Unknown Soldier's Tomb outside parliament.
No arrests or injuries were reported, and truckers said the violence was provoked by people who were not part of their protest.
Unionists said they planned to spend the night in front of the parliament building — where the proposed reforms are being debated over the next two days.
Brief scuffles broke out earlier as some protesters threw plastic bottles of water and cups of iced coffee at riot police, who responded with stun grenades.
"They must compensate us, pay us back the money we borrowed and mortgaged our homes to buy our licenses," driver Panagiotis Slivas said outside parliament. "There are already too many truck drivers ... we'll go out of business."
As night fell, the drivers, many holding Greek flags, sat in the street watching a parliamentary debate on the reforms on an outdoor screen, as food vendors set up carts nearby.
Giorgos Tsamos, leader of the fuel-tanker drivers' association, said the drivers were determined to confront the government.
"If the law (passes), we will continue our protest. The government has not delivered on any of its promises," he said.
Truckers have lined up their vehicles along highways and busy Athens roads since Sept. 13 to protest plans to abolish so-called closed-shop professions, which have jobs protected by fixed fees and rates and strict licensing rules.
The new rules will eventually affect a number of other professional groups, including pharmacists and civil engineers.
Truck drivers say the changes are too abrupt and will bankrupt those of their colleagues who have borrowed money to buy a truck license.
Transport Minister Dimitris Reppas rejected demands by the protest leaders to set a fixed price for the professional licenses, but insisted the government could grant them a tax break among other concessions.
"You cannot demand terms that shut people out of the profession. That doesn't happen anywhere in Europe," he said. "We are taking measures that will help professionals adapt to the new reality."
Greece has promised to reform its labor market as part of austerity measures agreed in return for euro110 billion ($144 billion) in rescue loans from European countries and the International Monetary Fund.
Labor unions fiercely oppose the austerity, arguing that less well-off Greeks are suffering disproportionately.
On Tuesday, the umbrella civil servant union Adedy called a 24-hour strike on Oct. 7, the eve of a hearing in Greece's highest administrative court of a legal challenge by unions and bar associations against the deal that secured the loans.
Also, workers at Greece's loss-making state railways will hold two five-hour strikes on Wednesday and Thursday to protest government plans to cut their salaries and open railways to private competition.
Opposition parties argue the government has mishandled the labor reforms, causing unnecessary hardship.
"You are breaking the backbone of Greek society," said Manolis Kefaloyiannis, a spokesman for the main opposition conservatives. "How can you bow down to some third-rate officials from the EU and the IMF? It's a disgrace."
Greece remains effectively blocked from borrowing on the bond market, due to high interest rates. But on Tuesday the government announced another successful sale of short-term debt.
The state debt management agency said it raised euro390 million by selling 13-week treasury bills.
The sale was oversubscribed by 6.25 times, with a yield of 3.98 percent — and together with successful debt auctions in Spain and Ireland, helped ease fears over Europe's debt crisis.
AP writer Nicholas Paphitis and AP Television's Amer Cohadzic and Eldar Emric contributed to this report.