Gunmen in Nigeria's oil-rich Niger Delta have attacked a vessel operated by the Exxon Mobil oil company, killing one crew member and wounding another.
The militants had been observing a ceasefire
The incident comes as three days of peace talks begin in Bayelsa State between local officials and militants.
Bayelsa State Governor Timipre Sylver told the BBC he was confident a deal would be reached that would address the militants' grievances.
They want more of Nigeria's oil wealth to be used to help local people.
The militant group, the Movement for the Emancipation of the Niger Delta, is expected to sign the peace deal on Friday.
However, the BBC's Alex Last in Lagos says it is not clear just who will participate - and whether they will include key players in the main militant organisation.
Nor is it clear what the terms of the deal are, he says.
Traditionally, peace deals and ceasefires in the Delta - of which they have been quite a few - have been secured through the promises of cash, contracts and employment, our correspondent says.
They have invariably turned out to be short-lived, when those with guns decided the terms were in need of improvement.
More importantly, the basic problems of the Delta - the proliferation of weapons, youth unemployment and poverty - will take years of good governance to address, says Alex Last.
Human rights groups say good governance in the Delta has long been in short supply.
Nigeria, an Opec member, is one of the world's biggest exporter of crude oil.
Disruptions to supply are one of the causes of the recent rise in oil prices towards $100 a barrel.
Violent attacks on oil company workers and installations have slowed since President Umaru Yar'Adua was elected in April on a promise to end the conflict.
This latest incident took place in Rivers State.
Security sources said the Seamark vessel was on the Bonny river heading for Onne when it was boarded by eight men from a speedboat, who shot one crewman dead and wounded another before ransacking the vessel.
Both men are Nigerians.