Gunmen kill 4 officers patroling waters in Bayelsa.

Police say gunmen have shot dead four police officers in Nigeria’s oil-rich southern delta.

The shootings follow a period of relative calm in the region, where a government-sponsored amnesty has appeased militants who once crippled the oil industry by targeting pipelines and expatriate workers.

Police spokesman Eguavoen Emokpae says the officers killed Thursday were on a boat patroling the Nembe river in President Goodluck Jonathan’s Bayelsa home state. It was not immediately clear if the gunmen shot from land or also were on boats.

“We lost four of our officers today in an attack launched by unknown gunmen. The policemen were on patrol on the waterways when they were shot and killed,” Emokpae said.

The policemen were killed at the marine police checkpoint on Nembe river in the southern state, he said.

No arrests were made, he said.

In another development, three members of the Joint Task Force (JTF), a military outfit deployed in the region to tackle crime, including oil theft and piracy, were also attacked by unknown gunmen in an ambush, an army spokesman said.

Colonel Timothy Antigha, spokesman for the JTF, who confirmed the attack, denied knowledge that the three military men were killed.

There had been unconfimed reports that the three — two soldiers and a naval rating — were killed in the attack.

“I am not aware that the three were killed. I know the attack took place when the team was going from Brass to Ogbia (in Bayelsa state). They were apparently ambushed. We are still gathering information on the incident”, he said.

Nigeria is Africa’s biggest oil producer and a top exporter to the U.S.

Foreign firms have pumped oil for more than 50 years out of Nigeria’s southern delta, but many Nigerians there believe their communities do not get the financial benefit they deserve from the industry.