A one-day cost-of-living strike in Belgium forced Brussels airport to cancel all outbound flights on Monday and halted many bus services across the country.
Unions said they expected tens of thousands of people to turn out for a protest in Brussels. Train services worked, in part to allow protesters to converge on the capital.
Brussels airport said it could not allow passenger flights to leave because the strike extended to security staff. Local public transport offered minimal services.
Inflation reached 9% in June in Belgium, reflecting sharp price rises elsewhere, largely because the Russian invasion of Ukraine has affected grain supplies and caused energy costs to rise.
Prime Minister Alexander De Croo said that Belgian workers are better protected than their counterparts in most European Union countries, as wages are indexed to inflation.
In statements to the public broadcaster RTBF, the Government has extended until the end of the year the measures to reduce the tax on sales of gas, electricity and fuel.