Human rights groups have raised concerns about the treatment of people arrested in the Sudanese capital, Khartoum, in recent days. The police crackdown follows an attack Saturday on the outskirts of the capital by rebels from the Justice and Equality Movement. Derek Kilner has more from VOA's East Africa bureau in Nairobi.

The New York-based organization Human Rights Watch says it is concerned about the treatment of those arrested since Saturday's attack and urged the government to act quickly to try or release those detained.

Official Sudanese media report that at least 300 people have been arrested in connection with the rebel attack, though many expect the number is higher. President Omar al-Bashir said those arrested will receive a fair trial.

Sudan's leading Islamist opposition leader Dr. Shaikh Hassan Al-Turabi talks to the press in Doha (File)

Islamist opposition leader Hassan al-Turabi, who has been suspected of ties to the Justice and Equality Movement, was detained for more than 12 hours on Monday. He has been released, but some members of his Popular Congress Party remain in detention.

There have been growing concerns that Sudanese security forces are rounding up people from Darfur who are living in Khartoum.

Jar Al-Nabi Abdul Karim, a field commander with a faction of the Sudan Liberation Army - another rebel group not involved in Saturday's attack - spoke to VOA from North Darfur.

"Someone contacted me from Khartoum yesterday. He told me there are many people from Darfur, from other tribes not only Zaghawa, they were being arrested. This is very bad. They do not have any relations with the attack by JEM. We demand the international community to help the people who the government arrested," said Karim.

Government spokesman Rabie Atti denies that the government is arresting civilians from Darfur.

"The security authorities and the police authorities are looking after the people who were involved in the attack," said Atti. "The government is not arresting Darfurians in general. That is not correct."

Khalil Ibrahim, the head of the Justice and Equality Movement (File)

Sudanese security forces continued their search for rebels it believes are hiding out in the outskirts of the capital, and a curfew remains in place in Omdurman, Khartoum's twin city across the Nile where Saturday's attack took place.

The government is in particular seeking the leader of the Justice and Equality Movement, Khalil Ibrahim, who is believed to have fled to North Darfur. The government has offered a hefty reward for his capture.

Meanwhile, the government of neighboring Chad has closed its border with Sudan, after President Bashir accused Chad of supporting the rebel attack.