( CNN ) -- Rebels in the oil-rich Niger Delta region said Friday they will launch new raids on oil installations to seize more hostages after Nigerian authorities freed 19 who had been seized . `` Our fighters have been instructed to carry out more raids on oil installations from where fresh hostages will be taken , '' the Movement for the Emancipation of the Niger Delta ( MEND ) said in a statement . The 12 Nigerians and two Americans , two Frenchmen , one Canadian and two Indonesians were released Wednesday . Nigeria has launched an ongoing offensive targeting Delta , Bayelsa and Rivers states , the largest military campaign in the Niger Delta since the government offered an amnesty program in 2007 . MEND is one of several militant groups in the Niger Delta that has been battling the government for years over the distribution of the country 's oil wealth . In its statement , the group offered its own version of the rescue operation , saying the fighters guarding the hostages retreated in order to prevent a gun battle that would have `` endangered the lives of these hostages . '' The group said the Nigerian military were tipped off to the location of the hostages by `` certain persons from this community , '' but did not elaborate . The statement ended with a threat : `` As earlier promised , we will soon commence with a all-out attack on oil installations across the Niger Delta . ''
The Nigerian military rescue 19 hostages . MEND is one of several militant groups battling the government . It says it will launch an all-out attack on oil installations .