PORT HARCOURT, Nigeria, July 10 (Reuters) - Nigerian troops repelled an attack on a construction site run by Korean firm Daewoo <047040.KS> in the Niger Delta in the early hours of Tuesday, killing some of the attackers, a military commander said.

The attack took place at Mbiama, on the outskirts of the delta's main city of Port Harcourt, where Daewoo are doing contract work for Italian oil firm Agip <ENI.MI>.

Daewoo staff including some foreigners live on the site and security contractors working for oil firms said the likely objective of the attackers was to kidnap some of the staff, although the military commander could not confirm this.

"Gunmen attacked the camp during the night. We fought back and some persons were killed," said Samuel Salihu, commander of the Joint Task Force responsible for security in the Port Harcourt area. He did not have an exact toll.

Abductions for ransom of foreign oil workers are extremely frequent in the Niger Delta, as are attacks on oil production facilities.

Oil output from Nigeria, the world's eighth-biggest exporter, is down by over 20 percent because of these attacks and thousands of expatriate workers and their families have left the region since the violence intensified at the start of 2006.

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