Gunmen aboard speedboats have attacked three oil services ships and kidnapped two Russian workers working for an aluminium company in separate incidents in Nigeria's Niger Delta.
The Falcon Crest and Falcon Wings were attacked on December 19 near crude oil facilities operated by Canada's Addax Petroleum off the coast of Nigeria's Akwa Ibom state. The captain on one of the vessels was killed in the incident.
It is believed the gunmen fled to nearby Cameroonian waters. No group has so far claimed responsibility.
A third ship, operated by Nigerian oil company Monipulo, was attacked by pirates early on December 20 near the Abana offshore oilfields.
Akwa Ibom, which shares a border with Cameroon, has seen an upsurge in maritime piracy and kidnappings in recent months. Six similar attacks on shipping in the region occurred earlier this year, the most recent incident two weeks ago.
In a separate incident on December 20 armed men in speedboats attacked a housing complex and seized two Russians working for an aluminium company ALSCON in the town of Ikot Abasi. ALSCON is owned by Russia's United Company RUSAL, the world's largest aluminium producer.
Attacks on oil production facilities and kidnappings of foreign workers for ransom are common in the region. Oil output in Nigeria, the world's eighth biggest oil exporter, has been reduced by about a fifth since 2006, when activists started a campaign of violent sabotage to push for their neglected districts to be improved.
Criminal gangs have exploited the instability in the country, financially supporting themselves through a profitable business in stolen crude oil and by kidnapping local politicians, businessmen and expatriates for ransom.
Since the militants began their campaign more than two years ago over 200 foreigners have been seized. Almost all have been released without harm.