Two television journalists were shot and killed in the US state of Virginia today in an attack during a live early-morning broadcast, and authorities said the suspected gunman was a former employee of the TV station.

The suspect, 41-year-old Vester Flanagan, shot and killed himself several hours later as police pursued him on a Virginia highway, police said.

The two journalists who were killed were reporter Alison Parker, 24, and cameraman, Adam Ward, 27, who worked for CBS affiliate WDBJ7 in Roanoke, Virginia.

The woman they were interviewing was wounded in the shooting.

The on-air shooting occurred around 6.45am local time (11.45am Irish time) during an interview for the morning news programme at Bridgewater Plaza, a Smith Mountain Lake recreation site with restaurants, shops, boating and arcades and holiday rentals.

The area is in the south-central part of the state, about 190km from the capital of Richmond.

The broadcast was abruptly interrupted by the sound of shots as Ms Parker and the woman being interviewing screamed and ducked for cover.

Hours after the shooting, someone claiming to have filmed it posted video online that appeared to be from the shooter's vantage point.

The videos were posted to a Twitter account and on Facebook by a man identifying himself as Bryce Williams, which was Mr Flanagan's on-air name.

The videos were removed shortly afterwards. One video clearly showed a handgun as the person filming approached the woman reporter.

WDBJ7 reported that Mr Flanagan was a former employee who was let go two years ago.

The station reported that he shot himself as Virginia State Police were closing in on his rental car on Interstate 66 in Fauquier County.

He was driving a rental car after leaving his own car at the Roanoke-Blacksburg Regional Airport this morning, the station reported.

The suspect refused to stop for police

In a statement, Virginia state police said the suspect refused to stop when spotted by a trooper and sped away.

"Minutes later, the suspect's vehicle ran off the road and crashed. The troopers approached the vehicle and found the male driver suffering from a gunshot wound," police said in the statement.

Asked on CNN if the station had been targeted or had been threatened, WDBJ7 President and General Manager Jeff Marks said, "Every now and then you get a crazy email or something and we'll look into it - nothing of this nature that any of us could recall."

He said the interview was to mark the 50th anniversary of the founding of Smith Mountain Lake, and the woman being interviewed was from the local chamber of commerce. She had been talking about the anniversary and tourism.

There was still no word from the hospital on the condition of the woman, identified as Vicki Gardner, executive director of the Smith Mountain Lake Regional Chamber of Commerce.

The station's broadcast showed Ms Parker interviewing Ms Gardner about the lake and tourism development in the area. Gunshots erupted, and as Mr Ward fell his camera hit the ground but kept running.

An image caught on camera showed what appeared to be a man in dark clothing facing the camera with a weapon in his right hand.

The station described the two dead journalists as an ambitious reporter-and-cameraman team who often filmed light and breezy feature stories for the morning programme.

"I cannot tell you how much they were loved," Mr Marks said.

They were both engaged to be married to other people.

Meanwhile, the White House has issued a rapid call for Congress to pass gun control laws, in the wake of the killings of the two journalists.

"There are some common sense things that only Congress can do that we know would have a tangible impact on reducing gun violence in this country," said spokesman Josh Earnest.