A maritime security company has warned shipowners of further violence in the Niger Delta in the coming weeks.

It was responding to a threat from Nigerian militant group Niger Delta Avengers (NDA) to target shipping unless it wins mediated talks with the government over the state's sale of crude oil.

MAST's Singapore general manager Ben Stewart said the NDA appear to be taking the place of terrorist organisation Members of the Emancipation of the Niger Delta (MEND).

But he added there are a couple of critical differences.

"MEND’s aim was to redistribute oil wealth more effectively; the NDA’s aim is to create a sovereign state in the Niger Delta," he said.

"In the case of the warning given it is likely the NDA are seeking the release of Nnamdi Kanu, the Biafran independence activist who was arrested in October last year, and who they have declared an affiliation to.

“Given his previous record, president Buhari is unlikely to want to negotiate. Further violence mainly targeting oil and gas infrastructure and support logistics should be expected in the Niger Delta over the coming weeks.”