Plantation, Florida: Federal authorities arrested a man in Florida on Friday suspected of sending at least a dozen parcel bombs to high-profile critics of US President Donald Trump days ahead of congressional elections, officials said.

Two federal law enforcement officials named the suspect as Cesar Sayoc, born in 1962. He was taken into custody in the parking lot of an AutoZone store in Plantation, near Fort Lauderdale, where two witnesses told Reuters they heard a loud blast at the time of the arrest.

Local television stations showed investigators using a large blue tarp to cover a white van that was plastered with decals and stickers, before removing it on a truck.

A federal law enforcement official said more arrests could follow. Another law enforcement source said charges would likely be brought by federal prosecutors in Manhattan.

The US Justice Department was due to hold a news conference at 2:30 p.m. EDT., a spokeswoman said.

No one had claimed responsibility for parcel bombs, which were denounced by authorities as terrorism, and came less than two weeks ahead of US congressional elections that could alter the balance of power in Washington.

Police found two of the suspicious packages on Friday addressed to US Senator Cory Booker and James Clapper, the former US director of national intelligence, officials said.

The 11th package was addressed to Booker, a Democratic senator from New Jersey, and was discovered at a mail sorting facility in Florida, the FBI said. A 12th package was addressed to Clapper at cable network CNN and was intercepted at a New York City post office, a federal law enforcement official said.

A thirteenth suspicious parcel was discovered addressed to Democratic US Senator Kamala Harris of California, CNN said.

A federal law enforcement official said earlier on Friday that the focus had intensified on Florida as a key location for the investigation and possible point of origin of the packages.

Police closed roads around the AutoZone parking lot where Sayoc was arrested, and helicopters flew overhead.

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.

Florida Governor Rick Scott said he had been briefed on developments in the investigation.

"ANY attempt to harm others is disgusting & has no place in Florida or our country," Scott wrote on Twitter. "I appreciate the hard work of law enforcement to bring swift justice to whoever is responsible for these cowardly acts."

CNN reported that Sayoc has a criminal history and ties to New York. Reuters could not immediately confirm the report. All the people targeted by the suspicious packages have often been maligned by right-wing critics. They included former President Barack Obama, former Vice President Joe Biden, former Secretary of State and presidential candidate Hillary Clinton and billionaire Democratic Party donor George Soros.

The Federal Bureau of Investigation (FBI) has said that at least five of the packages bore a return address from the Florida office of US Representative Debbie Wasserman Schultz, a former chair of the Democratic National Committee.

There has been an outcry from Trump's critics, who charged that his inflammatory rhetoric against Democrats and the press has created a climate for politically motivated violence.

After first calling for unity and civil discourse on Wednesday, Trump lashed out on Thursday at the "hateful" media. His supporters accused Democrats of unfairly suggesting the president was to blame for the bomb scare.

On Friday, Trump said the incidents were distracting from successful efforts by Republican candidates.

"Republicans are doing so well in early voting, and at the polls, and now this "Bomb" stuff happens and the momentum greatly slows - news not talking politics," Trump wrote on Twitter. "Very unfortunate, what is going on. Republicans, go out and vote!"

None of the devices detonated and no one has been hurt. They were believed to have been fashioned from bomb-making designs widely available on the internet, according to a federal law enforcement source. Still, investigators have treated the devices as "live" explosives, not a hoax, officials said.

Investigators have declined to say whether they were built to be functional. Bomb experts and security analysts say that based on their rudimentary construction it appeared the devices were more likely designed to sow fear rather than to kill.

But two federal officials involved in the investigation cautioned that it was too early to say whether the devices were incapable of firing or were deliberately designed to frighten rather than explode.

Two packages were sent both to US Representative Maxine Waters and to former US Vice President Joe Biden. Others targeted for parcel bombs included former Attorney General Eric Holder, former CIA director John Brennan and actor Robert De Niro.

"I thank God no one's been hurt, and I thank the brave and resourceful security and law enforcement people for protecting us," De Niro said in a statement. "There's something more powerful than bombs, and that's your vote. People MUST vote!"