Nigeria, which has been forced to shut in more than half of its oil output following rebel attacks and a workers’ strike, could lose its position as Africa’s top oil exporter to Angola.

The cumulative oil production outage for Africa’s most populous nation now amounts to more than 1.3 million barrels per day from its most recent output of about 2 million bpd.

The loss includes the most recent shut-ins from Exxon Mobil and Royal Dutch Shell, the top two foreign oil producers in Nigeria.

Exxon has lost 770,000 barrels of its crude oil production, or almost all of its Nigerian output due to a workers’ strike over a labour dispute. Yesterday rebels claimed Shell’s shut-ins in the Delta amounted to 350,000 bpd.

David Fyfe, from the International Energy Agency, said “Problems continue to beset substantial volumes of Niger Delta production. With a temporary hiatus in new deep water development, further problems in the Delta could indeed hamper total Nigerian exports.”