Nigeria has announced measures to deal with the chronic fuel shortage which means car drivers in the oil-producing giant have to queue for hours, sometimes days, for petrol.

Police and troops will be formed into a new monitoring unit, charged with keeping petrol off the black market.

Critics of the government say the illegal diversion of supplies abroad will only end when the official price of petrol in Nigeria - currently about ten US cents per litre - is allowed to float freely.

However, correspondents say raising fuel prices would be politically risky shortly before elections intended to restore civilian rule.