Lagos - Attackers have ambushed and opened fire on a police boat in the oil-producing region of southern Nigeria, leaving 12 police officers missing, authorities said on Saturday.
The attack on Friday came after a purported statement from the main militant group in the Niger Delta region, MEND, threatened to resume attacks over the conviction of alleged leader Henry Okah in South Africa.
Police however said there was no link and the ambush appeared to be related to a dispute between an ex-militant and his gang. Authorities said the attack in the swamps of Bayelsa state came while officers were escorting the ex-militant for his mother's burial.
Bayelsa police commissioner Kingsley Omire said it was too early to say whether the officers were dead.
"Twelve policemen are missing," Omire told AFP. "Three policemen were rescued, as well as the boat driver. They were able to swim across to the swamp."
Divers and other search teams were combing the area of the state known as Lobia 2, he said.
Omire said the ex-militant who accepted the government's 2009 amnesty deal had requested a police escort for the burial of his mother and authorities obliged.
One of the police boats broke down on the way and was a "soft target," he said.
Two speedboats arrived and there was an exchange of gunfire between the attackers and police, he said.
Omire believes the attackers were members of the gang linked to the ex-militant and who have alleged that he had not properly distributed amnesty payments.
Such disputes have occasionally broken out among gangs and former militant leaders in the region.
A South African court jailed Okah for 24 years on 26 March following his conviction over twin car bomb attacks on Independence Day in Abuja in 2010. Okah has permanent residency in South Africa.
Okah was an alleged leader of the Movement for the Emancipation of the Niger Delta (MEND), an umbrella group which claimed to be fighting for a fairer distribution of oil revenue in Africa's largest crude producer.