|Sudan's government claims al-Turabi maintains links with Darfur fighters involved in Saturday's raid [AP]|
The government imposed a curfew in Khartoum after Jem's attack.
The restrictions were partially lifted on Sunday but low-intensity clashes have continued in Omdurman, on the western bank of the Nile opposite Khartoum.
About 65 people are thought to have been killed so far.
Jem's attack marks the first time that the Darfur conflict has reached Khartoum in decades of conflict between the country's Arab-dominated rulers and fighters from far-flung regions.
Al-Turabi denied that he has any links to Jem.
The government accuses the Popular Congress Party of having links to Jem fighters.
Mahjoub Fadl, the press secretary for Omar al-Bashir, Sudan's president, claimed on Monday that authorities found documents confirming links between leaders of the Popular Congress Party and a Jem attack in Omdurman.
But al-Turabi told Al Jazeera: "When they mentioned they had evidences and documents, I told them to submit them to the courts and that I did not need to see them."
Al-Turabi was a key partner of al-Bashir in a coup that brought them to power in the 1980s.
The allies soon fell out and al-Turabi was jailed. He was released on the condition that he would stay away from political life.
Chad shuts border
Chad's government announced on Monday that it was closing its eastern border with Sudan.
The move came a day after Sudan broke off diplomatic relations with Chad, accusing its neighbour of involvement in the previous day's attack.
"We are now cutting our diplomatic relations with this regime," al-Bashir had said on state television.
"These forces [behind the attack] are all basically Chadian forces supported and prepared by Chad and they moved from Chad under the leadership of Khalil Ibrahim."
The Chadian government has denied "all involvement".
Sudanese forces continue to hunt for Darfur fighters in Khartoum, where a shooting incident on Monday sent workers fleeing in panic.
Exchanges of fire also could be heard on the outskirts of Omdurman.
An interior ministry official said some fighters were still holed up in parts of Omdurman and a curfew there had been extended indefinitely.
Government forces rounded up what they said were Darfuri suspects in civilian clothes.
Darfur groups said thousands of labourers from their region in western Sudan had been arrested and beaten.
Khalil Ibrahim, JEM's leader, said on Monday that his organisation was prepared to launch further attacks on Khartoum in an attempt to topple the Sudanese government.
"This is just the start of a process and the end is the termination of this regime ... Don't expect just one more attack," he told the Reuters news agency.
Source: Al Jazeera and agencies