What is the cause of the strike?

The Nigerian government is meeting trade union leaders in its latest attempt to end a week-long strike over the removal of a fuel subsidy. The unions have already rejected a government offer to reinstate less than half of the subsidy, saying prices must be restored to their previous levels. Petrol prices have doubled since the subsidy was removed two weeks ago. The strike has already cost the Nigerian economy billions of dollars in lost revenue and has caused several deaths in clashes with the police.
                                                                BBC 2012-1-15