Sudan's largest opposition bloc has joined calls by a wide array of political groups for President Omar al-Bashir to step down, turning up the pressure on the longtime autocrat after two weeks of street protests.

Nidaa al-Sudan, or Sudan's Call, said in a statement on Wednesday that it wanted Bashir and his administration to go and for a transition toward democracy to begin.

Nidaa al-Sudan comprises the Umma party of former Prime Minister Sadeq al-Mahdi and rebel groups in the western Kordofan and Darfur regions, and the Blue Nile region south of Khartoum.

Bashir, who seized power in a 1989 military coup, has ordered the use of force against protesters who have taken to the streets since December 19 to demand his ouster. Authorities also arrested nearly two dozen opposition leaders.

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