Gunman's attack kills 4 marines

A gunman opened fire at a recruiting center and another US military site in Chattanooga, Tennessee, on Thursday, killing at least four marines before he was shot dead by police.

Federal authorities said they were investigating the possibility that the double attack was an act of terrorism, but they added they had no evidence that any one other than a lone gunman was involved.

Authorities identified the killer as Kuwait-born Muhammad Youssef Abdulazeez, 24, of Hixson, Tennessee.

An official who declined to be named said there was no indication that Abdulazeez was on the radar of federal law enforcement before the shootings.

The attacks took place minutes apart, with the gunman stopping his car and spraying dozens of bullets first at a recruiting center for all branches of the military, then driving to a navy-marine training center seven miles away, authorities and witnesses said. The attacks were over within half an hour.

The gunman fired at the recruitment center from inside his car, but he left the vehicle to shoot the four marines at the training center, said FBI agent Ed Reinhold.

The names of the dead were not immediately released. Three people were reported wounded, including a sailor who was seriously hurt.

Reinhold said Abdulazeez had "numerous weapons". He said investigators have "no idea" what motivated the gunman, but added, "We are looking at every possible avenue, whether it was terrorism, whether it's domestic, international, or whether it was a simple criminal act.

"There is no indication at this point that anybody else was involved."

Within hours of the bloodshed, law officers swarmed what was believed to be Abdulazeez's house, and two females were led away in handcuffs.

Abdulazeez graduated from the University of Tennessee in 2012 with a bachelor's degree in electrical engineering.

The Islamic State group has been encouraging extremists to carry out attacks in the US, and several such homegrown acts or plots have unfolded in recent months. President Barack Obama pledged a prompt and thorough investigation. "It is a heartbreaking circumstance for these individuals who served our country with great valor to be killed in this fashion," he said.

Marilyn Hutcheson, who works across the street from the navy-marine center, said she heard a barrage of gunfire at 11 am. "I couldn't even begin to tell you how many," she said. "It was rapid-fire, like pow-pow-pow-pow-pow, so quickly. The next thing I knew, there were police cars coming from every direction."