The arrest of Gaddafi's son, Seif al-Islam was an important step for international justice in the interest of the victims in Libya, a spokesman of the International Criminal Court (ICC) said on Monday.

"The aim of this arrest is to prevent repetition of mass crime. We hope that this arrest will have a deterrent effect," spokesman Fadi El Abdallah told Xinhua.

The ICC believed this arrest gives a strong sign to Muammar Gaddafi, whose whereabouts is currently unknown as Libyan rebels pushed into the heart of Tripoli on Monday.

The ICC said it was too soon to speculate about the date of the trial of Seif al-Islam.

"The main issue is to ensure the surrender of the suspect in order to give him a fair proceeding. We don't have clear information when exactly the suspect is going to be brought to The Hague." El Abdallah added.

Seif al-Islam was captured during a rebel offensive over the weekend which saw the rebel forces break a six-month stalemate and close in on Tripoli from three directions.

Earlier media reports said the ICC was planning to contact the Libyan rebels on Monday over the transfer of the Seif al-Islam to The Hague

The ICC issued arrest warrants for Muammar Gaddafi, his son Seif al-Islam and Libyan intelligence chief Abdullah al-Senussi in late June. All three were charged with crimes against humanity.

"We hope that the warrants could contribute to impartial and fair trial in the world," El Abdallah said.