Gunmen disguised as priests have killed at least three soldiers in Bayelsa state, southern Nigeria. The soldiers were part of the Operation Crocodile Smile, aimed at safeguarding oil facilities in the oil-rich area, known as Niger Delta.

The gunmen where wearing white robes and red caps according to witnesses and local leaders, the BBC reported.

It is believed the attackers seized the soldiers' equipment at a jetty where a similar attack took place in 2015. No group has claimed responsibility for the latest attack.

Earlier this year, the Nigerian government deployed security forces in the Delta as attacks blamed on the Niger Delta Avengers (NDA) militants, the latest group to wage war against Nigeria due to perceived marginalisation in the area, have brought the country's oil production to a 30-year low.

NDA does not attack people, but targets only oil and gas facilities across the area. However, security analysts have warned that a recent military operation launched against NDA could spark retaliatory attacks against members of security forces and civilians.

Following repeated attacks that have undermined the economy of Nigeria, Africa's largest oil producer, the government claimed it had entered into negotiations with NDA, something the militants deny.

Shortly after President Muhammadu Buhari confirmed talks were taking place in July, NDA accused him of spreading false claims and claimed responsibility for an attack at a gas pipeline in Akwa Ibom state.

NDA has also denied claims that the federal government had reached a 30-day truce with militants. The group urged Buhari to visit the country's south-east to witness the scale of damage caused by years of oil spills.

Nigeria up close: Check out our Flipboard magazine

Birth of militants in Niger Delta

Militant groups in the oil-rich Niger Delta region took hold in the early 2000s following the deterioration of living conditions blamed on the increase of oil-related activities by foreign exploration corporations. Tensions flared up in the local communities as some ethnic groups felt they were being exploited and did not benefit from the crude oil on their land.

The repeated oil spills that considerably damaged the environment and affected people's health further deepened the communities' frustrations. After being elected in 2015, Buhari extended a 2009 amnesty granted to 30,000 former militants in the area.