A Nigerian government spokesman says nine South Koreans taken hostage by Nigerian militants Wednesday have been freed.

The spokesman says the hostages were released Friday unharmed.

It was not immediately clear if a Nigerian kidnapped with the South Koreans had also been released.

All 10 men are employees of a South Korean company, Daewoo Engineering and Construction. Gunmen seized them early Wednesday from a residential compound on the outskirts of Yenagoa, the capital of Bayelsa state.

This was the second time in less than a year that South Korean workers in Nigeria were kidnapped.

Attacks and kidnappings are common in Nigeria's oil-rich Niger Delta region. Militant groups are pressing the government to give local communities more of the region's oil wealth.

Some information for this report was provided by AFP and Reuters.