Iraqi Kurds ran the ring which between May and November charged migrants 2,000 euros ($2,180) each to hide them in lorries heading to England, the police said in a statement.
"The gang operated very frequently, almost daily, and smuggled a large number of people every day, up to 20 people per night, or hundreds of people per month," police said.
"The result of this Belgian investigation, carried out with the help of the British authorities, can be considered a big blow in the fight against organised people smuggling."
The smugglers hid the migrants in lorries, many of them refrigerated and potentially dangerous, as they were parked at night along highways near the Belgian capital Brussels or between Ghent and Antwerp, the country's main port, police said.
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Ghent prosecutors' spokeswoman Eva Brantegem said the two suspected ring leaders were arrested in Britain last week in cooperation with Britain's National Crime Agency. Belgium has asked for their extradition.
Police added that 10 Iraqi Kurdish men suspected of participating in the ring were already in custody after being arrested in Belgium between May 22 and November 25 last year.