By Andrew Heavens
KHARTOUM (Reuters) - Riot police arrested three senior members of south Sudan's main political party and more than 100 supporters who demonstrated around Sudan's parliament on Monday despite an official ban, witnesses and officials said.
The three men were later released and two -- the Sudan People's Liberation Movement's (SPLM) Secretary General Pagan Amum and his deputy Yasir Arman -- received a hero's welcome at their party's headquarters in downtown Khartoum, according to a Reuters witness.
The SPLM and opposition parties had called the rally to demand democratic reforms ahead of next year's elections in a rare public challenge to President Omar Hassan al-Bashir's dominant northern National Congress Party (NCP).
Sudanese authorities announced on Sunday that the rally was banned.
The SPLM is junior partner in the national coalition government formed by a 2005 peace deal that ended more than two decades of civil war between Sudan's north and south.
Arman was detained after scuffling with police early on Monday outside the parliament, said a Reuters witness. The SPLM later said police also arrested Amum and Sudan's state interior minister Abbas Juma, an SPLM member.
Hundreds more banner-waving supporters gathered in the area and other parts of Khartoum's Omdurman suburb after the arrests and were dispersed by police using tear gas.
"The situation is brutal. More than 100 SPLM members have been arrested and many more other protesters have been detained," SPLM spokeswoman Keji Roman told Reuters.
Senior NCP official Ibrahim Ghandour said the protest had not been banned by his party, but by Sudan's Interior Ministry which declared it illegal because organizers had failed to apply for permission to hold the event.
"The National Congress Party is not against democratic action including protests and rallies," he told Reuters.
Security services had also decided to stop the rally because of "information received ... on the intent of the circles organizing of the demonstration to perpetrate anarchy and to use molotov bombs," NCP official Mandour el-Mahadi told Sudan's state Suna news agency
SPLM leader and south Sudan's President Salva Kiir said the arrests were "provocative and unjustified" in a statement.
Senior SPLM official Anne Itto said the news sparked anger in the south, where attackers set fire to the NCP's headquarters in Wau, the capital of Western Bahr el Ghazal state. She had no reports of injuries.
An official in the opposition Umma party had said on Sunday the ban showed the NCP was not serious about letting dissenting voices take part in elections, scheduled for April 2010.
The oil-producing country is to hold its first multi-party polls in 24 years under the 2005 peace deal that created the SPLM-NCP coalition government.
Relations between the former foes have stayed tense and both have accused each other of failing to implement the deal, which guarantees the south a referendum on independence in 2011.
Two million people were killed and 4 million fled their homes between 1983 and 2005 as Sudan's north and south battled over differences of ideology, ethnicity and religion.
(Additional reporting by Khaled Abdel Aziz in Khartoum and Skye Wheeler in Juba; Editing by Giles Elgood)