Thousands of protesters have descended upon Brussels, Belgium to express their displeasure over the European Union’s (EU) austerity budget programs as EU leaders meet in the city to discuss how to stabilize the euro zone finances.

Belgian police have fired water cannons and tear gas on the demonstrators who threw bottles and stones at them.

The originally peaceful protests escalated into a violent confrontation when a group of demonstrators entered the Rue de la Loi, a street near to the locale of the EU summit. As the group increased in size, police appeared and clashed with the protesters. Then activists blocked some key roads and created a traffic gridlock.

Trade unions across the continent are particularly incensed by budget cuts since they aim to lower wages.

The European Commission's annual examination of growth as well as the competitiveness pact launched by German Chancellor Angela Merkel and French President Nicolas Sarkozy will drag wages and social rights down to dangerous levels, said Belgium's in a statement.

A spokeswoman for Belgium’s Socialist FGTB union said about 15,000 protesters were expected to show up for the rally, although police said about 12,000 attended.

Protesters are also angry about an expected plan by EU officials to hike retirement ages and make labor markets for flexible.

At the level of pensions, social security and work flexibility, what has been put on the table at the European level is unacceptable, Myriam Delmee, vice-president of the BBTK union in Belgium, told Reuters.