(Adds details, quotes) By Estelle Shirbon ABUJA, May 17 (Reuters) - Nigerian unions have called for a two-day strike on May 28-29 to protest against widespread vote-rigging in last month's elections, union leaders said on Thursday. The strike, which will coincide with the inauguration of president-elect Umaru Yar'Adua on May 29, will not affect oil production, they said. Nigeria is the world's eighth-biggest exporter of crude. "Everybody is expected to stay at home because the action involves not only the unions but also many civil society organisations," said John Kolawale, secretary general of the Trade Union Congress (TUC). He was speaking just after a meeting of leaders from the TUC and another umbrella labour organisation, the Nigeria Labour Congress (NLC). Kolawale said representatives from more than 30 civil society groups also took part. The NLC has called April's elections "fundamentally flawed and therefore unacceptable". The polls were supposed to deliver the first democratic transition from one civilian president to another in Africa's most populous country, but international observers said fraud was so widespread that the results were "not credible". May 29 is a public holiday in Nigeria known as "Democracy Day". Union leaders said the point of striking on that day was more to demonstrate popular discontent over electoral fraud than to disrupt any economic activity. "That very day the attention of the world will be on Nigeria and we want to show that the swearing-in of Yar'Adua is a farce and it is not a true reflection of what democracy is," said Peter Esele, who is president of both the TUC and PENGASSAN, one of the main oil unions. Yar'Adua's inauguration is due to take place that day at a military parade ground in the capital Abuja, where preparations are already going on for a lavish ceremony. "May 29 is supposed to symbolise democracy, but we do not have a true democracy in this country," said Esele. Official results gave the ruling People's Democratic Party a landslide victory although dozens of candidates for legislators' and state governors' posts are contesting the results in court. The NLC had already called for mass protests on May 1 and thousands of demonstrators gathered in the main cities, but the rallies were tightly controlled by security forces who arrested and teargassed scores of activists. Since then, popular protests have been muted.
