Indonesia's separatist Free Aceh Movement (Gam) has vowed to fight on despite the arrest of three of its exiled leaders in Sweden.
Mr Mahmood (front L) and Mr Abdullah (front R) are in detention
The men were arrested on Tuesday and prosecutors said they were suspected of "crimes violating international law".
A spokesman for the movement told the BBC that Gam remained "firm and steadfast" in the wake of the arrests.
Jakarta is waging a big anti-insurgency campaign in Aceh, where more than 2,000 people have died in the last year.
The men who Swedish authorities have taken into custody have been identified as Malik Mahmood, known as prime minister inside the Free Aceh Movement, and Zaini Abdullah.
A third man, Hasan di Tiro, is still at his home for medical reasons.
They had been under investigation for more than a year after Indonesia asked Sweden to take action against them.
They came to Sweden in the early 1980s as political refugees, and are now all Swedish citizens. As such they cannot be extradited to Indonesia.
Details of their alleged crimes are unclear.
Bakhtiar Abdullah, spokesman for Gam in Sweden, said this lack of information was very worrying.
"We are very concerned about the arrests of three of our leaders because we don't know exactly why they have been arrested or where they are being held," he told BBC News Online.
But he added that Gam respected the Swedish judicial system. "We are giving all the co-operation needed to the Swedish Government," he said.
Jakarta has said the three men under investigation are responsible for a blast in the Jakarta Stock Exchange in 2000 which killed 15 people, as well as several other bombings and assassinations.
Indonesia welcomed the Swedish authorities' move.
"The government appreciates the steadfast commitment and concrete actions taken by the Swedish Government... against individuals who are suspected to be instigating acts of armed rebellion in the territory of Indonesia," the Indonesian Foreign Ministry said in a statement.
Mr Abdullah said the arrests would not dim the group's fight for independence from Jakarta rule.
"Our people are still firm and steadfast. It is nothing that we have to be panicked about," he said.
"All the leadership, not just in Sweden, but also back home, are carrying on their duties as usual."
Aceh's rebels have been fighting for independence for their oil-rich province for the last 27 years.