THREE PEOPLE HAVE been killed and 27 are in hospital after a wooden boat capsized during a possible human smuggling operation just off the US San Diego coast.

Local lifeguards, the US Coast Guard and other agencies responded following reports of an overturned vessel near the peninsula of Point Loma, according to the San Diego Fire-Rescue Department.

Three people died at the scene and 27 people were taken to hospital with “varying degrees of injuries,” department spokesman Jose Ysea said.

Ysea said when he arrived at the scene near the Cabrillo National Monument there was a “large debris field” of broken wood and other items in the choppy waters.

“In that area of Point Loma it’s very rocky. It’s likely the waves just kept pounding the boat, breaking it apart,” Ysea said.

Lieutenant Rick Romero, from San Diego Lifeguard Services, said seven people were pulled from the waves, including three who drowned.

One person was rescued from a cliff and 22 others managed to make it to shore on their own, he added.

Romero said: “Conditions were pretty rough: five to six feet of surf, windy, cold.”

Officials said the group was overcrowded on a 40-foot (12-metre) cabin cruiser that is larger than the typical open-top wooden panga-style boats often used by smugglers to bring people illegally into the US from Mexico.

“Every indication from our perspective was this was a smuggling vessel. We haven’t confirmed their nationality,” said Jeff Stephenson, a supervising agent with US Border Patrol.