Sudan on Monday freed the country's top opposition leader, who was jailed for nearly seven weeks after calling on President Omar al-Bashir to surrender to face war crimes charges.

The release of Hassan Turabi, a senior Islamist ideologue, appeared to be an attempt to blunt opposition to the president, who is trying to rally support at home after an international tribunal issued a warrant for his arrest on charges he was behind atrocities in Darfur.

Upon his release, Turabi remained critical of the president's defiance of the International Criminal Court and of the government's expulsion of aid groups in retaliation for the warrant. But he did not repeat his outright call for the president's surrender.

The 76-year-old's deteriorating health was a factor in the release, said his son, Siddique Turabi. Party members said negotiations and pressure on the government also played a role.

Looking tired and slightly thinner than normal, but smiling brightly in his white traditional robes, Turabi received hundreds of well-wishers at his home in Khartoum, Sudan's capital.

Asked by The Associated Press if he thought al-Bashir would eventually have to surrender, he said, "It will take time probably. ... All human beings under pressure, of course, ultimately respond."

Turabi said al-Bashir will have to deal with the court sooner or later, saying the warrant is "difficult" to avoid. Al-Bashir has rejected any dealing with the Netherlands-based ICC, refusing even to seek a year-long freezing of the case against him.

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"They (government leaders) are in a state of crisis now. So they behave a little temperamentally," Turabi said. "It is better to solve the conflicts in court, instead of solving them in the streets with more conflict."

Turabi also criticized Khartoum's expulsion of 13 international aid groups from Darfur a day after the warrant was issued. "This is not a correct measure. ... These groups worked for many years and supported Sudan," he said.

Turabi said al-Bashir should back efforts by Arab and African countries to convince the U.N. Security Council to freeze the case for a year.

Al-Bashir is accused of directing attacks against civilians in Darfur, the vast arid region of western Sudan where up to 300,000 people have died and 2.7 million have been driven from their homes, according to the U.N. The government rejects the ICC and the charges against al-Bashir.

The conflict began six years ago with an uprising by ethnic African rebels accusing the Arab-dominated government of neglect and discrimination. Sudan's government responded with a counterinsurgency and is accused of unleashing militia fighters who have carried out atrocities.

Turabi was arrested Jan. 14, two days after telling reporters that al-Bashir should give himself up to the Netherlands-based court to save Sudan from internal strife. He was held without charge, and no official reason was given for his arrest, but supporters said it was punishment for his remarks.

There was no immediate comment from the government Monday. Another leader of Turabi's Popular National Congress Party was also released.

Turabi was once an ally of al-Bashir and was the driving force behind a 1989 military coup that brought the president to power. The two fell out in 1999, and Turabi set up his own party. He has been jailed several other times.

The government has accused him of fomenting the rebellion in Darfur. He is believed to be the mentor of the leader of Justice and Equality Movement, the most prominent of Darfur's numerous rebel groups.

Turabi is popular among many in Darfur, and his release could give al-Bashir a reprieve among domestic critics. There were some early signs of such a softening among opponents.

A senior member of Turabi's party, Ibrahim al-Senousi, said the release "brings the government out of a crisis" as it seeks to unify public opinion. He said Turabi and his party have not changed their opinion about the court, but that they could support the government in resolving the Darfur conflict and bringing people to justice.

"His release ... helps in easing the tension, and people can work together to see how to resolve this," al-Senousi said.