President Paul Biya has blamed the opposition for violence which has left at least seven dead in Cameroon.
There have been scenes of unrest in Douala since the weekend
Protests, sparked by a fuel price rise, continued despite a government decision to scale back the increase.
Police tear gassed stone-throwing youths in the capital, Yaounde, who had set up burning barricades.
Correspondents say protesters are also angry about suggestions President Biya might amend the constitution to try to extend his 25 years in power.
In a televised address on Wednesday evening, the president accused political opponents of trying to force him from power.
He said some people were trying to obtain through violence what they had failed to achieve through the ballot box.
He used colourful language as he described those behind the violence as "the apprentice sorcerers in the shadows" who, he said, did not care about the consequence of their actions.
"What we're looking at here is the exploitation... of the transport strike for political ends," said President Biya.
The BBC's Randy Joe Sa'ah in the city of Douala says a taxi-drivers strike was called off on Tuesday night after the government agreed to a small reduction in the price of fuel.
There are plans for Mr Biya to run for president again in 2011
But the unions have lost control of the situation and the violence has not ended, he adds.
Protesters are demanding more cuts in the price of food and fuel.
Police in Douala clashed with some 2,000 protesters as they tried to cross a bridge, causing about 20 to fall into the river below, our reporter says.
Tear gas was also used to quell demonstrations in other cities like Bamenda and Yaounde.
Opposition groups have been calling for protests to stop the constitution being amended to allow Mr Biya to run for re-election when his current term expires in 2011.
On Saturday, tear gas and water cannon were used to disperse hundreds of opposition supporters in Douala.
The day before, the government had announced the closure of private television station Equinoxe, which has broadcast interviews with politicians opposed to plans to change the constitution.
The BBC West Africa correspondent Will Ross says Cameroon is home to more than 100 different ethnic groups, and keeping the country relatively stable has been one of the major achievements of President Biya's time in office.
The violent scenes across the country this week are a sign that the population is becoming increasingly frustrated in what is one of the most corrupt countries in Africa, he says.