Guinea-Bissau's interim president said on Tuesday the impoverished West African nation could sink into political chaos, as fears of unrest grew after an ousted former ruler declared himself president, Reuters reported. Former leader Kumba Yalla, overturned in a bloodless coup in 2003, said at the weekend he was the rightful head of state, raising the spectre of violence in the coup-prone nation ahead of presidential elections due on June 19. Hundreds of Yalla's supporters, some wearing red woollen hats like those favoured by the former leader, gathered on Tuesday outside his house, which is guarded by soldiers. It was not immediately clear whether a scheduled march would go ahead. "There is a serious risk of political chaos," interim President Henrique Rosa told a news conference. "Subjugating the superior interests of the nation ... to the objectives of a battle for power based on political radicalism, dangerous confrontation and the discredit of institutions, constitutes a serious offence," he said. Yalla, a former philosophy professor, said on Sunday he had only renounced power under duress. His bid to return has set the former Portuguese colony on edge. --more 2321 Local Time 2021 GMT