Brussels, Belgium (CNN) -- Strikes by trade unions in Belgium disrupted travel Monday on the Eurostar and Thalys international train lines, the companies announced, as European leaders gathered in the capital Brussels for an informal summit.
Eurostar passengers trying to get to Brussels from London had to change from trains to buses in Lille, France, on Sunday night and Monday, the company announced. Eurostar "strongly advised" passengers to rebook travel for another day.
Thalys cancelled dozens of train services to and from major European destinations including Paris and Amsterdam because of the Belgian strike.
But CNN journalists in Brussels Monday did not see protests Monday morning or notice major traffic disruptions as a result of the strike.
One of Belgium's main unions, known as FGTB in French and ABVV in Flemish, said the strike was necessary because negotiations with the government were going slowly and not producing specific results.
The general strike was necessary, the union said January 17, "to convince the government and employers to keep in mind the social reality of employees and social welfare recipients."
Belgium's government is trying to bring down its budget deficit.
CNN's Jim Boulden, Antonia Mortensen and Theo Nikolaou contributed to this report.