Nigeria is bracing for mass protests against what is widely seen as a flawed presidential election that gave the ruling party an overwhelming victory.

Opposition groups have rejected Nigeria's electoral commission results from the country's local and national elections in April. They are calling for rallies to be held across the country Tuesday, when the west African nation commemorates Workers' Day.

The opposition will join labor unions and social groups for rallies across the country, with the largest protest planned for the capital, Abuja.

Meanwhile, police in Abuja have met with union leaders and issued a ban on political protests during the May Day celebrations. Abuja police chief Lawrence Alobi told VOA that the ban aims to preempt widespread violence.

The elections ensured a landslide win for the governing People's Democratic Party, which has ruled Nigeria for eight years.

Independent election observers, however, say fraud was so widespread that the balloting lacked any credibility.

The European Union's chief election monitor in Nigeria, Max van den Berg has said some 200 people were killed during Nigeria's electoral process, although there has been no other confirmation of that figure.

Nigeria's opposition parties have been strongly critical of the electoral commission, saying it mishandled the elections and should be dissolved.

Some information for this report was provided by AP and Reuters.