Tensions between Sudan’s Radical Islamist Ansar Al-Suna sect and Sufi groups heated up ahead of common celebrations of Prophet Muhammad’s birthday in Sudan’s twin capital city of Omdurman.

Authorities barred Ansar Al-Suna from celebrating the holiday in Omdurman’s al-Khalifa square after the group threatened violence against more than 50 Sufi groups already celebrating there.

Violent clashes between followers of the two rival sects on Sunday left two people injured. Tensions heated up on Monday night, when more than a dozen of people were injured in a violent brawl and Sudanese police had to use tear gas to break up the crowd.

A Sufi leader Muhammed Akhmed told RIA Novosti Monday’s brawl began when an Imam from Al-Suna started to criticize Sufi followers at a common sermon. The Sufis responded by throwing stones at Ansar Al-Suna’s tent.

Tensions between the two groups, whose views and interpretation of Islam vary in many ways, have increased in the recent past, the Sudan Tribune wrote.

In late 2011, a number of Sufi shrine sites in Al-Ailafon suburb, 35 km east of Khartoum, were destroyed and burned by suspected members of Ansar al-Suna.