Lagos, Nigeria (CNN) -- Nigerian authorities have freed 19 hostages seized by rebels in the oil-rich Niger Delta region, a military spokesman said Thursday.
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.
Authorities recovered an anti-air gun, rocket-propelled grenade launchers, 30,000 rounds of ammunition and dynamite "often used to blow up pipelines," said Lt. Col. Timothy Antigha, spokesman for the Joint Task Force formed to combat rebels.
There were no casualties but the military encountered "certain amount of resistance," he said.
The Movement for the Emancipation of the Niger Delta (MEND) claimed responsibility for the kidnapping of of seven people earlier this month. It was unclear whether those hostages were among those freed.
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.