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An Indonesian court sentenced a radical Muslim cleric to four years in prison Tuesday for plotting the overthrow of the government, but the judges acquitted him of leading Jemaah Islamiyah (search), a Southeast Asian terror group linked to Al Qaeda.

The mixed result and the lenient sentence for Abu Bakar Bashir has thrown an unclear light on the efforts of the world's most populous Muslim nation to crack down on terrorism and Islamic militancy.

"In order that the defendant does not repeat his mistake ... he must be punished," said Judge Muhammad Saleh. "We, the judges, hand down a sentence of four years in prison."

Prosecutors had asked the court to sentence Bashir to 15 years in jail, instead of demanding the maximum life sentence.

The trial was politically sensitive for President Megawati Sukarnoputri (search), whose coalition government depends on the support of moderate Muslim parties.

Representatives of these parties, including her own vice president, Hamzah Haz, have in the past expressed support for Bashir.

In a sometimes contradictory six-hour decision by a five-judge panel, Saleh said there was insufficient evidence to support the principal charge that Bashir was head of Jemaah Islamiyah, which is blamed for a string of bombings across the region.

"The defendant ... had knowledge of an organization that is trying to topple the government," Saleh said. "That is why the secondary charge has been proven."

Bashir was also found guilty on the lesser charge of entering Indonesia illegally in 1999.

Bashir, 65, said he would appeal the verdict. "I cannot accept the judgment," he said.

The trial was seen as a key test of Indonesia's commitment to confronting Islamic militancy. Last month, a special court in Bali sentenced to death a Muslim radical for his role in last year's terror attacks on two nightclubs in which 202 people died.

The verdict was initially greeted by joyous cheers from hundreds of Bashir's supporters, who had mistakenly believed that their leader had been cleared of all charges. After the trial ended, some followers chanted "Hang America."

Prosecutors tried to link Bashir to Jemaah Islamiyah, which is said to be seeking to establish a fundamentalist super-state in Southeast Asia. But Bashir insisted that the group did not even exist and denied any wrongdoing, saying the charges against him had been fabricated by the United States and Israel.

Bashir, who teaches at a religious boarding school in Central Java, was arrested in the immediate aftermath of the Oct. 12 Bali bombings. He was not been charged with involvement in that attack or the Aug. 5 bombing of Jakarta's JW Marriott Hotel that killed 12 people.

But prosecutors said that under his leadership, Jemaah Islamiyah plotted to kill Megawati and establish a hardline Islamic regime.

Defense attorneys earlier challenged prosecutors' use of testimony from suspects held without trial in Singapore and Malaysia under draconian internal security laws.

The attorneys claim key testimony was obtained under torture, and that the witnesses -- who addressed the judges via video-link -- should instead have been brought to Indonesia to speak freely in open court.

"There was not a single proof that Bashir intended to topple the government," Adnan Nasution, Bashir's defense lawyer, said after the verdict.