An explosion has rocked the Liberian capital, Monrovia, leaving at least four people dead.

The BBC's Sam Howard in Monrovia says that some eye-witnesses said it was caused by a landmine, while others spoke of a hand grenade or a gas cylinder.

The blast occurred at a warehouse where scrap metal is stored in the western suburb of Siryontown.

Charles Taylor is the subject of a UN ban

Police have arrived on the scene but have not accused any group of responsibility.

Two more people are seriously injured. All the victims worked at the warehouse.

Our correspondent says the blast caused panic as residents feared it was an attack by the Liberians United for Reconciliation and Democracy (Lurd) rebels.

They have approached Monrovia twice this year before being beaten back by government troops.

President Charles Taylor is the subject of an international arms ban by the United Nations after his support for rebels in neighbouring Sierra Leone.

He says this is preventing him from getting enough weapons to defeat Lurd forces.