The move by General Sanni Abacha, who seized power from a civilian head of state in November, is the latest escalation in a showdown between the military dictatorship and a growing opposition movement.
General Abacha said he was sacking the executive councils of the two national oil unions - Nupeng and Pengassan - and of the Nigerian Labour Congress, the trade association that represents 5 million industrial workers. He is to replace them with military-appointed administrators. The rare speech to the nation was broadcast on national television and radio.
Union leaders who have been expecting such a ban have warned they would organise an underground resistance to the government. Frank Korkori, head of Nupeng (the National Union of Petroleum and Natural Gas Workers), denounced the speech. General Abacha had jailed Mr Korkori at the outset of the strike then was pressured to free him. 'It is our intention to fight this arbitrary dictatorship,' he said. 'The government has no right to dissolve us. We have sent signals to all our branches to ignore it.'
Nigeria has been in crisis ever since the military annulled the 12 June 1993 presidential election apparently won by Moshood Abiola. The election was aimed at ending a decade of military rule. Chief Abiola was arrested after declaring himself president to mark the first anniversary of the election. Oil workers went on strike in protest on 4 July, crippling the country's main industry.
'It is a selfish motive, ruthless in execution and sadistic in expectations,' General Abacha said of the oil strikes. He also said he would not free Chief Abiola, who is on trial for treason, claiming it was up to the government-controlled court system to determine whether he should be freed.
Since toppling a civilian figurehead in November, General Abacha has dissolved all elected legislatures, closed respected newspapers and jailed human rights activists and politicians critical of his regime. But he has not been able to contain the oil strike, which has cut Nigeria's vital oil production in half and triggered fuel shortages across the country.