Why had the national Congress of Trade Unions called for a strike?

The national Congress of Trade Unions had called for a strike on Tuesday and Wednesday (July 3-4) to protest against a 70 percent hike in the fuel price in Zimbabwe. Labor Minister July Moyo was quoted by state media as saying the strike is illegal. Wellington Chebebe, trade union secretary general, said the movement’s general council was determined that the strike should go ahead. In his words "With immediate effect, the labor movement has now put the issue of national protest on its agenda." Mr. Moyo claimed the union had what he termed "ulterior motives" but he did not say what these were. Nor did he specify the laws under which the strike was being banned, beyond saying the union should have informed the government first.