Exiled Darfur rebel leader Abdelwahid Nur vowed Friday, on the eve of south Sudan\'s independence, to topple the Islamic regime in Khartoum and replace it with a secular state like the south. \"We congratulate our colleagues and brothers in south Sudan in advance of their independence day,\" said Nur, who heads a branch of the Sudan Liberation Movement, one of the main Darfuri rebel groups. \"We are going to liberate north Sudan and create a liberal, secular and democratic state... equal to south Sudan,\" he told AFP on the telephone. \"It is our mission... to change this Islamic fundamentalist regime. The war will not be in Darfur, it will be in Khartoum,\" he said, and called on \"all groups in north Sudan\" to join his movement and help it to achieve its goal. Observers say opposition to the centre from Sudan\'s neglected peripheral regions like Darfur may grow in the wake of southern secession. Khartoum has often accused the southern authorities of backing rebel groups in the war-torn western region, where the present conflict first erupted in 2003 between non-Arab rebels and Sudan\'s Arab-dominated government. South Sudan denies the claims, and in turn accuses the north of arming southern militias in a bid to destabilise the region, as it did during the devastating 22-year civil war between Khartoum and southern ex-rebels turned ruling party the SPLM. The head of the northern branch of the SPLM, Malik Agar, warned on Sunday that if Khartoum failed to halt its military offensive in the embattled state of South Kordofan, there could be a \"coordinated\" rebellion from Blue Nile state in the east to Darfur in the west.