The unions doubt the rally will draw as many as the more than 100,000 people who protested in November 2014 against the austerity policies of Prime Minister Charles Michel’s government, which had come to power a month earlier.

However, organisers expect tens of thousands of people to rally in the capital Brussels on Tuesday morning.

It is designed to pave the way for a mass public services rally and a rail strike on May 31, as well as general strikes on June 24, September 29 and October 7.

The FGTB, CSC and CGSLB unions oppose proposed reforms from Employment Minister Kris Peeters allowing employers to impose 45-hour work weeks.

“Everybody will be hurt very much by the abandonment of the 38-hour week, the increased recourse to temporary workers, the absence of coordination, the under-financing of (public services) or pensions,” FGTB official Michel Meyer told Le Soir newspaper.

A month after the mass anti-austerity protest in November 2014, trade unions brought Belgium to a standstill as the biggest general strike in years grounded flights, cut international rail links and shut ports.

There were sporadic incidents of violence during both events.

The latest union actions come two months after the March 22 Islamic State suicide bombings that killed a total of 32 people at Brussels airport and a metro station near the European Union headquarters.

The government has come under fire for alleged security lapses in those attacks as well as in the November 13 Islamic State gun attacks and suicide bombings that killed 130 people in Paris.

The government has also been unable to end a near month-long strike by prison staff and mobilised the army to fill the gaps.