Two Indonesians suspected of having links to the Bali bombings and an attack on the Australian Embassy in Jakarta are being interrogated in East Java.
News of their arrest came as the Indonesian parliament ratified two international treaties the government says will help it fight the global war on terrorism.
Deputy national police spokesman Anton Bahrul Alam said officers caught Arif Hermansyah and Ahmad Basyir Umar on Friday and would decide their status soon.
Alam said the two men had close links to Noordin Top and his slain partner Azahari Husin, leading operatives of the al-Qaeda linked Jemaah Islamiah militant group, which is blamed for the Bali bombings.
"These arrested two are old players. We have seven days from the date of arrest before we decide whether they could be suspects," he said, adding both were arrested in the East Java city of Surabaya.
"We believe Arif gave (explosives) to Noordin M Top prior to the Kuningan bombing," Alam said, referring to the 2004 bomb attack at the Australian Embassy, located in Jakarta's busy Kuningan district.
Alam added police believe Umar hid Top and Azahari before the latter was killed during a police raid last year in the East Java retreat area of Batu.
Top, whom authorities believe is an expert in recruiting young suicide bombers among Indonesia's poor, has become South-East Asia's most wanted Islamic militant since the death of Azahari, Jemaah Islamiah's alleged chief bombmaker. Police believe Top is still on Java, Indonesia's main island.
Indonesia's parliament, meanwhile, has ratified two global treaties against terrorism – the 1999 International Convention for the Suppression of Terrorist Financing and the 1997 International Convention for the Suppression of Terrorist Bombing.
"Only with effective international cooperation can terrorism be eliminated," Foreign Minister Hassan Wirajuda told the parliament. "Our support for these two conventions will smooth that cooperation and strengthen our legal institutions and capacities in combating terrorism." Wirajuda did not mention when the president would give his final seal to conclude the ratification process.
Indonesian authorities have blamed Jemaah Islamiah for a number of major bombings against Western targets in the world's most populous Muslim country in recent years.
Top and Azahari, both from Malaysia, have been key players in most of the attacks, police say.
A number of junior militants linked to Top have been arrested in the past months, but Indonesian officials and Western governments say Top and his followers are still a threat, despite the arrests and the killing of Azahari.