Residents of Juba, Southern Sudan, registering to vote. (Photo Courtesy UN Photo/Tim McKulka)

The top United Nations envoy in Sudan has voiced his concern over the detention and alleged beating of some prominent Sudan People's Liberation Movement (SPLM) leaders, opposition supporters and civil society activists during demonstrations earlier today, noting that they could impact negatively on the 2005 peace pact that ended the country's north-south civil war.

Ashraf Jehangir Qazi, the Secretary-General's Special Representative and head of the UN Mission in Sudan (UNMIS), also expressed concern about the reported setting on fire of National Congress Party (NCP) offices, according to a statement.

He noted that these developments come at a "very critical" stage in negotiations between the SPLM and the NCP on issues related to the 2005 Comprehensive Peace Agreement (CPA), which includes a provision for a referendum on independence for the south slated for 2011, following national elections next year.

"He emphasized the central importance of political rights and freedoms, especially in the lead-up to elections and referendum," said the statement.

While welcoming the subsequent release of SPLM leaders as well as First Vice-President Salva Kiir's call for calm and restraint, Mr. Qazi urged all concerned authorities to take measures to ensure that law and order is maintained and acts of political violence are prevented.

"He called on both parties to give the highest priority to bringing about a conducive political environment for the successful implementation of the CPA."

Secretary-General Ban Ki-moon stated in a recent report that the key to implementing the CPA is the relationship between its signatories, the NCP and the SPLM, and called on both sides to boost cooperation.