Nigeria has lost $4.4bn in oil revenue in the past year due to increasing violence in the Niger Delta region.
A range of gangs and militant groups operate in southern Nigeria
Finance Minister Nenadi Usman blamed cuts in oil exports on the activities of militant groups demanding more control of Nigeria's oil revenue.
Meanwhile five Chinese workers, kidnapped in the volatile Niger Delta last week, are said to be safe.
"According to what we know, all five are still safe," Chinese government spokesman Liu Jianchao told reporters.
"The Chinese government, relevant departments and our embassy in Nigeria are expending all efforts to find a way to secure their release."
The Chinese telecommunications workers were abducted by unidentified armed men early last Friday in oil-rich Rivers State.
Kidnappings have become common in the region where armed militant groups are demanding greater share of the oil wealth coming from the swamps of the delta.
Mrs Usman told reporters at a news conference in Abuja that crude oil production had fallen by as much as 600,000 barrels per day in the second quarter of last year.
"The loss was due principally to social disruptions in the Niger Delta," she said,