President Umar Yar'Adua has said the trade in stolen oil is akin to the trade in "blood diamonds", fuelling a conflict in the country's oil-producing south and destabilising the government. Estimates to the volume stolen annually range from tens of thousands to hundreds of thousands of barrels per day. When oil prices were tipping at $147-per-barrel it was a multimillion-dollar-a-day industry. Oil theft, known as "bunkering", is connected to drug smuggling and gunrunning. A number of armed militia groups operate in the Niger Delta. Militants claim to be fighting for a better distribution of Nigeria's oil wealth, but armed groups fund themselves with oil theft, extortion and kidnapping.