Security forces stormed the headquarters of the Umma National Party, lead by former prime Minster Sadeq el-Mahdi, on Tuesday, detaining several dozen top leaders and confiscating property after the party rejected demands it cancel the anniversary celebrations.

Mohamed el-Mahdi, party official, told the Associated Press on Thursday that all the members were released except for two persons -- one of them the head of Sadeq el-Mahdi's office. The confiscated property was also returned, he said.

Before their release, however, the party's vice president -- Adam Madibu -- and some of their other detained leaders were summoned by Sudan's Crimes Against the State Department and were warned they would be prosecuted if they tried to go ahead with unlicensed activities, the official Sudan Media Center reported.

The party leaders promised to seek licenses for any gatherings, said Mohamed Farid, head of the department, quoted by the Media Center.

The Umma party had planned to hold celebrations marking the anniversary of an April 6, 1985 coup that ended the military rule of Gaafar Nimeiri in Sudan. The revolt was followed by the first free election since 1969, bringing the Umma leader el-Mahdi, to the prime minister's post.