The head-on collision, which happened on Monday morning, injured almost 150 other people, 55 seriously.
Eurostar cancelled its trains in and out of the Belgium capital, and its Lille services has run with delays.
The French high-speed Thalys services to France, Germany and the Netherlands have also been affected.
In a statement on its website, Eurostar said: "We advise that if you do not need to travel to Brussels on Tuesday 16 February that you defer or cancel your trip.
"You will be able to exchange your tickets for a later date or have them refunded."
Eurostar's services to Paris remain unaffected.
Lille services normally run to and from Brussels, and Eurostar said a "very limited" capacity shuttle bus had been used to transfer passengers between the two cities. Its website also listed alternative rail routes.
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