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 .
Eurostar and Thalys international train services are affected . Unions say the strike is necessary because government works are proceeding slowly . CNN journalists do not report strikes or major traffic disruptions .