Oil prices topped 50 US dollars a barrel for the first time today.

The cost of crude in New York passed the psychologically important landmark overnight and continued to rise to reach 50.47 US dollars a barrel as a string of events worldwide conspired to keep traders on edge over supplies.

Political unrest in Nigeria's oil producing region, continued instability in the Middle East and the effect of hurricanes in the Caribbean have put pressure on prices, which have risen steadily over the last week.

With global oil demand estimated to be 82 million barrels a day, energy analysts put the amount of excess oil production available at about 1%.

Yesterday, Brent crude - oil found in the North Sea and traded on the International Petroleum Exchange in London - hit a new high at 46.28 US dollars, before settling back to close at 45.93 US dollars.