Hellman made the statement while commenting on speculation that Lukic could be transferred from an extradition prison in Argentina to Belgrade.
He recalled that the ICTY's Office of the Prosecutor recently requested that Lukic's case be referred to the State Court of Bosnia-Herzegovina.
The ICTY will decide on the matter in a foreseeable time, Hellman added.
In the case of war crimes against non-Serbs in the area of the eastern Bosnian town of Visegrad, along with Lukic, the ICTY also indicted his relative Sredoje and Mitar Vasiljevic, who has been sentenced to 15 years in prison and is serving his sentence.
Lukic is charged with extremely cruel killings and inhuman treatment.
The most drastic cases include locking up large groups of Muslims in houses which were then set on fire, Hellman recalled.
The spokesman for the Office of the High Representative in Bosnia-Herzegovina, Kevin Sullivan, said Lukic's arrest was exceptionally important because in the past three months there had not been any concrete results in bringing war crimes indictees to justice.
He stressed that the Bosnian Serb authorities were now expected to engage more and meet their share of obligations regarding full cooperation with the ICTY.
The Sarajevo-based daily "Dnevni avaz" has reported that Lukic was tracked down in Argentina by BIA, a secret service of Serbia and Montenegro.
Minister Rasim Ljajic of Serbia and Montenegro, who is in charge of cooperation with the ICTY, has said the latest arrest is the result of operations carried out over the past nine months by Serbia and Montenegro's secret services.
The Bosnian Serb interior ministry said after the news of Lukic's arrest was confirmed that the operation was the result of intensive intelligence and operative measures conducted by the ministry in cooperation with the police forces of Serbia and Montenegro and the international community.
The NATO headquarters in Banja Luka issued a statement saying that the arrest was the result of direct pressure exerted by NATO, local authorities and the international community with the aim of bringing to justice persons indicted for war crimes.