Turkey, however, has indicated that it would welcome President Omar al-Bashir, who will reportedly arrive in Istanbul on Monday for a meeting of the Organization of Islamic Conference, a bloc of Muslim countries.

"It would be a disgrace for Turkey to offer him safe haven," Amnesty International senior legal adviser Christopher Keith Hall said. Human Rights Watch said Turkey's international image will suffer if it welcomes al-Bashir.

The Hague-based International Criminal Court issued a warrant against al-Bashir in March, accusing him of orchestrating atrocities in Sudan's western Darfur region.

Turkey is not a state party to the court and is not legally bound to arrest al-Bashir. It is a non-permanent member of the U.N. Security Council, which urges states to assist the court.

Turkish authorities have responded to questions about al-Bashir's visit by noting that visitors to the Islamic conference will attend an international event, not a bilateral one.

On Friday, Turkey's Hurriyet newspaper quoted President Abdullah Gul as saying al-Bashir was coming for a "special meeting" and that outside interference in the matter was inappropriate.

Turkey is engaged in a struggling effort to join the European Union, which would oppose a visit by al-Bashir. It is expanding its contacts with other Muslim and regional countries, carving out a foreign policy that is distinct from its Cold War-era loyalty to the West.

Iranian President Mahmoud Ahmadinejad, whose country is locked in a dispute with the West over its nuclear activities, is also expected to attend the Islamic forum in Istanbul.