Washington DC: Democratic presidential nominee Joe Biden on Sunday denounced the alleged harassment of one of his campaign buses by Donald Trump supporters on a Texas highway, in an incident the FBI confirmed it is investigating.

Video posted on Twitter appears to show multiple trucks with Trump flags surrounding and slowing the Biden/Harris bus.

The president himself tweeted a video of the incident late Saturday, saying, "I LOVE TEXAS."

The FBI said on Sunday it was investigating an incident in which a convoy of vehicles flying flags in support of President Donald Trump’s re-election bid surrounded a bus carrying campaign staff for Democratic challenger Joe Biden on a Texas highway.

Biden staffers were rattled by the event, the source said, though no one was hurt. Neither Biden nor his running mate, California Sen. Kamala Harris, were on the bus.

Staffers on the bus called 911, which eventually led to local law enforcement assisting the bus to its destination.

Meanwhile, Trump again defended the supporters who surrounded Biden’s campaign bus, saying that they ‘escorted’ the bus.

"They escorted the bus. And the radical left said 'oh what a horrible thing that is, to escort the bus.'" They're just people with an American flag and a Trump flag,” Trump said.

On the other hand, Biden told reporters in Texas Sunday evening, "We've never had anything like this."

"At least we've never had a president who thinks it's a good thing," he said.