Indonesian police say they have arrested the new spiritual leader of the radical South-East Asian Islamic group Jemaah Islamiah (JI).
Abu Bakar Ba'asyir's treason trial started on Wednesday
Abu Rusdan is among 18 suspected JI members arrested in the past week, three of whom are wanted in connection with the Bali bombings last October, which killed more than 200 people.
Police in Jakarta claim Mr Rusdan replaced radical Muslim cleric Abu Bakar Ba'asyir as head of JI, which some foreign governments have linked to the al-Qaeda militant network.
News of the arrest came on Wednesday, the opening day of Mr Ba'asyir's trial for treason.
He is accused of plotting to overthrow the Indonesian Government in order to turn the country into an Islamic state.
If convicted, he could spend the rest of his life in jail.
Erwin Mappaseng, head of Jakarta's criminal investigation
department, said Abu Rusdan is thought to have taken over as head of the JI network when Mr Ba'asyir was arrested in the wake of the Bali bombings last October.
JI is widely believed to have been behind that attack, as well as a string of other bombings in the Asian region.
I do not accept the charges... These are lies from
Mr Rusdan was captured in the central Java town of Kudus, early on Wednesday morning.
Of the other 17 detainees, one is thought to be Malaysian national Nasir Abbas, an alleged regional JI leader.
Another three are wanted in connection with the Bali attacks, and have been named as Syawab, who allegedly helped assemble the bombs, Umar Besar, whose photo-fit was released last year, and Ahmad Rohim.
Police also claim to have found guns, ammunition and a hand-made bomb similar to that used in the Bali explosions.
Ba'asyir in court
Abu Bakar Ba'asyir began Wednesday's court proceedings by denying all the charges against him.
ABU BAKAR BA'ASYIR
Has praised Osama Bin Laden
Runs an Islamic school in Java
Denies links with terrorism
Entering the courtroom looking relaxed and happy, he was met by crowds of supporters, who sent up a cry of Allahu Akbar - God is Great - as he was led to the dock.
The radical cleric, with his trademark white beard, white robes and skullcap, stared impassively as his accusers read out the 25-page indictment against him, says BBC correspondent Rachel Harvey, who attended the court session.
The indictment against Mr Ba'asyir does not name him as a suspect in the Bali attack, but relates principally to a series of church bombings on Christmas Eve 2000, which killed 19 people.
Mr Ba'asyir has also been charged in relation to an aborted bomb attack in Singapore in 2001, as well as immigration violations and giving false statements to police.
But the cleric insists he is being made a scapegoat by a government determined to restrict the activities of true Muslims.
"I do not accept the charges. These are lies from
America," Mr Ba'asyir said of the allegations against him.
The trial has now been adjourned until next week, when Mr Ba'asyir's lawyers are expected to respond to the charges.