PLANTATION, Fl., Oct 26 - FBI agents arrested a 56-year-old man in Florida on Friday suspected of sending more than a dozen parcel bombs to high-profile critics of US President Donald Trump days ahead of congressional elections, authorities said.

Agents who took Cesar Sayoc into custody in Plantation, near Fort Lauderdale, also hauled away a white van that was plastered with pro-Trump stickers, the slogan "CNN SUCKS" and images of Democratic figures with red crosshairs over their faces.

A federal law enforcement source said the van belonged to Sayoc. Two witnesses told Reuters they heard a loud blast as he was detained in the parking lot of an AutoZone store. Justice Department officials were due to hold a news conference at 2:30 p.m. EDT. (1830 GMT).

Announcing the Federal Bureau of Investigation arrest to a cheering audience at the White House, Trump said such "terrorizing acts" were despicable and had no place in the United States.

"We must never allow political violence to take root in America - cannot let it happen," Trump said. "And I'm committed to doing everything in my power as president to stop it and to stop it now."

According to public records, Sayoc is a registered Republican and has been arrested numerous times over the years including one case in which he was accused of making a bomb threat.

A federal law enforcement source said charges would likely be brought by federal prosecutors in Manhattan.

No one claimed responsibility for the parcel bombs addressed to former President Barack Obama and others, which authorities denounced as terrorism. The episode came less than two weeks before US congressional elections that could alter the balance of power in Washington.

Four more suspicious packages were found on Friday, according to officials and media reports, bringing the total to 14. None of the devices has detonated, and no injuries have been reported.

The intended recipients of packages discovered on Friday included Democratic US Senator Cory Booker of New Jersey, former US Director of National Intelligence James Clapper, Democratic US Senator Kamala Harris of California and Democratic donor Tom Steyer.

Hours after a federal law enforcement official said the investigation's focus on Florida had intensified, police closed roads around the AutoZone parking lot in Plantation where Sayoc was arrested, and helicopters flew overhead.

A man named Dre, a manager at a used car dealership next door to the AutoZone, said he heard a loud noise that sounded like an explosion shortly after 11 a.m.

"I opened the door and saw the FBI there," Dre, who declined to give his full name, said in a telephone interview.

A woman who lives nearby and declined to give her name said she was in her yard weeding on Friday morning when she heard a loud bang, saw smoke and heard a lot of shouting.

TV images showed investigators there using a blue tarp to cover Sayoc's van before removing it on a truck.

Reuters