Protesters blocked traffic outside the European Union headquarters in Brussels, and clashed with the police over the Belgian government's austerity plans on Monday. Workers also stopped public transport and threw hundreds of eggs at the headquarters of the Flemish nationalist N-VA party, a member of the governing coalition - leading to scuffles between protesters and police. Most schools, businesses and government offices remained closed through out the day.

"There has never been a strike this strong," Marie-Helene Ska, the head of the CSC union was quoted by the Belga news agency, and reported by AFP.

Air traffic controllers joined in the strike, forcing the closure of Belgian airspace. No plane was able to land or take off from airports in Brussels, Liege, Charleroi, Antwerp and Ostend for 24 hours, starting on Sunday night.

Brussels international airport cancelled a total of 600 flights, affecting some 50.000 passengers, according to airport spokeswoman Florence Muls.

"All flights are canceled. Everything is immobilized," Muls told AFP.

International train traffic was also severely affected, including high-speed rail services Eurostar and Thalys. Railway signal cables were also set on fire in Brussels, which is expected to cause more disruptions on Tuesday. The railway workers' CGSP union denied any involvement and called the incident "sabotage."

The port of Antwerp was also blocked, with more then 50 ships unable to enter or leave.

Too much debt

Monday's general strike was the culmination of a series of regional work stoppages, after the government of Prime Minister Charles Michel refused to change its austerity plans. They include raising the retirement age and skipping a public sector wage increase which was due in 2015. The government also intends to introduce public sector cutbacks, with the aim of saving 11 billion Euros ($ 13,7 billon) in the next five years.

Belgium is already at risk of EU disciplinary proceedings over a large public debt.

Belgian unions, however, oppose the reform and launched a protest movement last month with a march of more than 100,000 people in Brussels, which left dozens of police officers injured.

Marc Goblet of the FGTB union told private broadcaster RTL that there could be further labor actions in January, if the government and employers continued with "the same autistic logic" as reported by the DPA news agency.

dj/pfd(AFP, dpa, Reuters)