Pirates captured a South Korean-flagged fishing vessel off the coast of Somalia on Tuesday and efforts by a U.S. Navy ship and a Dutch vessel to intervene were abandoned when members of the South Korean crew were threatened with guns and the ship slipped into Somali territorial waters, the Navy said.

Cmdr. Jeff Breslau, spokesman for the U.S. Navy's 5th Fleet in Bahrain, said he did not know the number of crew aboard the South Korean vessel, the Dong Won.

It was the latest in a series of incidents off the coast of Somalia. On March 18, two U.S. Navy ships exchanged gunfire with suspected pirates, killing one and wounding five. No U.S. sailors were injured. Somalis involved in that incident later claimed they were patrolling Somali waters to stop illegal fishing when the U.S. ships fired on them.

On Tuesday morning, naval ships patrolling international waters in the Persian Gulf region as part of an international Maritime security mission received a radio distress call from the Dong Won, which reported that it had been fired upon about 60 miles off the coast of Somalia, according to a statement issued by 5th Fleet.

Some hours later the guided missile destroyer USS Roosevelt and the Dutch ship HNLMS Zeven Provincien arrived at the scene. Apparently, by that time the pirates had taken control of the fishing vessel.

Breslau said that when the Dong Won turned toward Somali territorial waters, one or both of the U.S. and Dutch ships tried to intercept it and fired warning shots in its direction. Members of the South Korean crew were seen on the deck of the Dong Won with guns pointed at them, so the intercept effort was broken off, he added.

"The top priority is the safety of innocent lives," the 5th Fleet statement said.

Breslau said the U.S. and Dutch ships remained in the area in international waters to monitor the situation.