Washington, Jul 17 (IANS): Four soldiers were shot dead by a gunman at US military offices in Chattanooga and Tennessee in an act of "domestic terrorism", authorities said. The lone attacker too was later gunned down.

The shooting incidents, which lasted for about 30 minutes, took place around 11 a.m. on Thursday at a National Guard office and a Naval Reserve centre about 10 km apart. The shooter reportedly shot while driving in an open-top Mustang, Xinhua news agency reported.

The shooter, identified as Muhammad Youssef Abdulazeez, worked as a security guard for the Chattanooga's public works department, CBS News reported, although later reports said that it is his father who works there.

The network, citing sources with security agencies, said that Abdulazeez, who was killed in the second attack, was 24 years old and a US citizen of Kuwaiti descent.

It was an act of "domestic terrorism", said US District Attorney Bill Killian at a press conference. The four soldiers were killed at the Naval Reserve centre, according to Efe news agency.

A local police officer was among the three people injured. The shooter was gunned down by local law enforcement personnel, Chattanooga Mayor Andy Berke said.

Homeland Security Secretary Jeh Johnson said in a statement that the agency was closely following the incident and its aftermath and is supporting the investigation, which is being headed by the US Federal Bureau of Investigation (FBI).

"We will treat this as a terrorism investigation until we determine it was not," said Ed Reinhold, an FBI special agent in charge of the investigation, at a press conference. "We have not determined if it was an act of terrorism or a criminal act."

Reinhold added that the gunman, with "numerous weapons" on him, appeared to act alone, adding that the gunman did not work at the military facilities involved.

Assistant White House spokesman Eric Schultz said that President Barack Obama, who was on an official visit to Oklahoma, had been informed of the incidents by his national security team.

After receiving a briefing from FBI Director James B. Comey, Obama said: "We don't know yet all the details, but we know that it appears that a lone gunman carried out these attacks. We have identified a name."

"It is a heartbreaking circumstance," the president said, speaking at the White House after returning from Oklahoma, adding that a full investigation would be conducted into the incident.

Abdulazeez reportedly lived in Hixon, a small town on the outskirts of Chattanooga.