Jakarta - Indonesian President Susilo Bambang Yudhoyono warned Friday that terrorism remained a threat to the country despite various achievements in combating such attacks.

In a state of the nation address ahead the August 17 independence day, Yudhoyono said efforts to thwart and overcome transnational crime and terrorism have shown "encouraging progress."

"The security apparatus has managed to arrest, prosecute and sentence the perpetrators," Yudhoyono said, adding that police discovered a cache of home-made explosives and bombs in South Sumatra's capital of Palembang in July.

"Various achievements are very heartening to all of us, but we must continue to heighten our vigilance," he said.

Indonesia has been hit by a string of terrorist attacks in the past few years, including the 2002 Bali bombings which killed more than 200 people, mostly foreign visitors.

After initially being in denial about its home-grown terrorism problem, the Indonesian government has made tremendous strides since the 2002 Bali bombings against Jemaah Isamiya (JI), a Muslim militant group inspired by Osama bin Laden. Authorities have arrested more than 400 suspects and convicted most of them, and severely damaged JI's ability to operate.

In addition to the bombings on Bali in 2002 and 2005, JI is also blamed for several simultaneous church bombings across Indonesia on Christmas Eve 2000; the bombing of the JW Marriott in Jakarta in 2004 and the one at the entrance to the Australian Embassy in 2005.

Indonesia's constitutional court on Thursday opened hearings into a motion by lawyers for three Bali bombers on death row asking the court to reconsider the method of their executions by firing squad, a move seen by many as another effort to delay the execution.

The three, Amrozi, known as the "smiling assassin," Imam Samudra and Ali Ghufron - who are being held in an island prison off Java - have asked to be beheaded instead of shot and claim they are eager to die as "martyrs" for their Islamist cause. (dpa)