Anti-austerity protests by Belgian and European labor organizations and security measures deployed ahead of a European Union summit have shut down traffic in parts of Brussels.

Marches by demonstrators early Thursday clogged this capital's main thoroughfares, especially those leading to the neighborhood where the headquarters of several EU's institutions are located.

Some 10,000 demonstrators congregated around midday in Brussels' EU Quarter, where the heads of state of government of the 28-nation bloc will meet on Thursday and Friday.

Belgian police opted to close several streets and tunnels to avert traffic chaos in the city, while authorities have urged people to use public transport and avoid driving or even walking in the area affected by the protests.

The demonstrators belong to 50 citizens' groups and labor organizations that have united under the "Alliance D19-20" banner (referring to the dates of the summit) to protest EU-wide austerity measures and euro-area economic coordination imposed by Brussels.

Austerity measures favored by Germany and other northern European countries are deeply unpopular and viewed as counter-productive in other parts of the eurozone, particularly among workers in Spain and Greece, which are struggling with sky-high unemployment rates.

Demonstrators also oppose a proposed U.S.-EU free trade and investment agreement currently being negotiated in Washington, saying the talks are being held in secret and without the consent of the general public.

They say EU economic-coordination and budget agreements and the Transatlantic Trade and Investment Partnership will have a negative impact on European workers' quality of life.

During the two-day summit, European leaders are expected to discuss ways to strengthen economic cooperation and boost growth and employment, as well as promote the development of a credible and effective Common Security and Defense Policy.

They also will address other matters such as Europe's immigration challenges and ongoing international crises in the Ukraine, the Central African Republic and Syria. EFE