In Nigeria, authorities are intensifying efforts to free foreigners who have been trapped on offshore oil rigs by striking oil workers since the middle of April.
Negotiations are continuing at several levels to end the protest by Nigerian workers against the U.S. company Transocean.
The Nigerian navy, the main union representing Nigerian oil workers and Transocean are all taking part.
Transocean operates the four rigs on which the 100 foreigners, mainly Americans and Europeans, are being held.
The Nigerian navy says some of its forces are in the area off the country's south coast, where the foreigners are being held. Navy officials say they are ready to take action, but that it would be better if the crisis could be resolved through dialogue.
Jake Molloy, a labor union leader who represents some of the foreign workers held captive, says they have become increasingly isolated.
"I've got no means of communicating with anybody," he said. "The guys' access to [communications] are now restricted to one phone call, generally in the evening, and, obviously, the lads are using that to call their wives and family. So, I've been unable to get anything since Monday morning."
Previously, Mr. Molloy said, the captives wrote e-mails complaining of excessive heat and lack of water. One captive wrote he feared for his life.
While these kinds of incidents are common among multinational oil companies in Nigeria, they usually end peacefully, after a period of negotiations.
The disgruntled Nigerian workers began their protest April 16, after Transocean fired five Nigerian union members for alleged theft and corruption. Transocean has been refusing to reinstate the five workers. It is not known if those who took part in the protest action will also be fired.