Singapore has arrested two men it alleges were being groomed as future leaders of the militant Muslim group Jemaah Islamiah (JI).
Singapore said both belonged to a cell set up by JI suspect Hambali
The two, both Singaporean nationals, were members of the same Pakistan-based cell that was broken up in September.
Six Indonesian men from the cell were extradited to Indonesia this month and a further five are being detained in Malaysia.
Singapore said the arrest of the two Singaporeans had "dismantled" JI's operations in the city state.
Singapore's Ministry of Home Affairs said Muhammad Arif bin Aaharudin, 20, and Muhammad Amin Bin Mohamed Yunos, 21, were being detained under the country's Internal Security Act.
Singapore said the two studied at a JI-run religious school in Malaysia in the 1990s, and had both received military training.
"Both Arif and Amin were among several students who were talent-spotted by the JI leadership to be groomed to become the next generation of key operatives and leaders in the JI organisation," the ministry said.
The Pakistan cell is reported to have been set up by Riduan Isamuddin, better known as Hambali, who is believed to have been JI's operations chief but is now in United States custody.
Hambali's brother, Rusman Gunawan, has been accused of running JI operations in Pakistan and is one of the six Indonesians handed over to Jakarta.
Indonesian authorities said on Thursday that two of the six had been released for lack of evidence.
Under Indonesian law, the remaining four must be released by Friday unless evidence against them can be found.
JI is suspected of carrying out a string of bombings in the region, including the Bali attacks in October 2002.