The Pompei's crew was released after 10 weeks in captivity when the ship's owner paid a reported $3 million ransom. Belgium caught two pirates involved in the hijacking, convicted them and sentenced them to nine and 10 years in prison.
But prosecutors still wanted the ringleaders.
"Too often, these people remain beyond reach while they let others do the dirty work," Delmulle told reporters.
Malaysian authorities almost captured the reclusive Adbi Hassan in April 2012, but a document from the Somali transitional government let him slip back home, according to a U.N. report last year that called him "one of the most notorious and influential" leaders of a piracy ring that has netted millions in ransom.
So Belgian authorities decided to go undercover to get him, because they knew he traveled very little and that an international arrest warrant would produce no results in unstable Somalia.
They approached an accomplice known as Tiiceey, dangling a fake job as an adviser to a fake movie about piracy, Delmulle said.
The two men took the bait. Tiiceey was also arrested Saturday.
The prosecutor refused to divulge any more details of the sting. The two Somalis were to appear in court Tuesday in Brugge.
