Last year, with assistance from the US and Brazil, Liberian security officials seized a container with more than 500 kilos of cocaine inside.

Four men - from Liberia, Portugal, Lebanon and Guinea-Bissau - were arrested in what was seen at the time as one of Liberia's biggest successes against drug smugglers.

But last week a jury in the capital Monrovia found them not guilty.

The justice minister condemned the decision, saying it had brought international ridicule on Liberia. He vowed to re-arrest them but they have since fled.

Liberian authorities have launched a manhunt for the suspects.