New York City Mayor Bill de Blasio called attempted attacks on CNN and top Democrats, including Barack Obama and Hillary Clinton, “an act of terror”.
Suspected bombs were sent to locations in New York, the Washington DC area and Florida, authorities said on Wednesday.
Mr de Blasio told reporters it was an effort to terrorize and “to undermine our free press and leaders of this country through acts of violence”.
The FBI says the ongoing investigation is “of the highest priority”.
It has identified five similarly constructed packages and devices to date, including one confirmed to be a pipe bomb found at the home of liberal philanthropist and financier George Soros two days ago.
CNN’s New York office was evacuated on Wednesday morning after a suspected live bomb was sent to their mailroom.
Speaking at the White House, President Donald Trump said that these threats “have no place in America”.
“The safety of the American people is my highest and absolute priority,” he said.
“In these times we just have to unify. We need to come together and send one very clear unmistakable message that threats or acts of political violence of any kind have no place in America.”
All the apparent targets are regularly criticised by conservatives – especially by President Trump.
Some Democrats have accused the president of inciting violence with his past rhetoric, while some of his supporters have said they believe the packages are part of a Democratic plot to win votes in the mid-term elections.
There is no evidence for this and the police have not released any information about any suspects.
The attempted attacks come just under two weeks before the vote, with US politics highly polarised.
What has the reaction been?
On Wednesday, White House spokeswoman Sarah Sanders condemned the “attempted violent attacks” against the public figures. She then specified in a follow-up tweet that the White House also condemned threats made to CNN.
But CNN worldwide president Jeff Zucker criticised President Trump and Mrs Sanders in a statement on Wednesday afternoon.
“There is a total and complete lack of understanding at the White House about the seriousness of their continued attacks on the media,” he said.
“The president, and especially the White House Press Secretary, should understand their words matter. Thus far they have shown no comprehension of that.”
The president has repeatedly called journalists, and CNN in particular, “fake news” and the “enemy of the people”. Last week he praised a Republican congressman who had assaulted a reporter with a “body slam”.
In a joint statement, top Democrats Nancy Pelosi and Chuck Schumer also said the president’s latest words “ring hollow until he reverses his statements that condone acts of violence”.
New York Mayor Mr de Blasio added during a news conference: “To all public officials, to all partisan affiliations – don’t encourage violence, don’t encourage hatred, don’t encourage attacks on media you can disagree but you have to show respect.”
Who were they sent to?
Explosive devices were sent to the following individuals, according to the latest FBI statement:
- Former Secretary of State Hillary Clinton
- Former President Barack Obama
- Former CIA Director John Brennan, care of CNN
- Former Attorney General Eric Holder
- George Soros (on Monday)
The devices are suspected to be pipe bombs. None of them exploded.
The ones addressed to Mr Obama and Mrs Clinton were intercepted by security services before they were delivered.
They were all sent in manila envelopes with bubble wrap, addressed with computer-printed labels. Each listed Debbie Wasserman Schultz, former chairwoman of the Democratic National Committee, as the sender, although her name was misspelt.
In a statement, the Florida congresswoman said she was “deeply disturbed” by the way her name was used.
The package addressed to Mr Brennan was sent to CNN as he was scheduled to appear on the network on Wednesday, US media report.
New York Police Commissioner James O’Neill also said law enforcement is analysing an “envelope containing white powder” that was found in the packaging of that device sent to CNN.
An additional suspicious package addressed to Democratic Representative Maxine Waters is also being investigated by local law enforcement and the FBI.
US media say the package intended for Mr Holder was sent to an incorrect address and returned to the congresswoman’s office in Sunrise, Florida.
What have the apparent targets said?
Speaking at a campaign event in Florida, Mrs Clinton thanked the Secret Service and said she and her family “are fine”.
“It is a troubling time,” she said. “It is a time of deep divisions and we have to do everything we can to bring our country together. We also have to elect candidates who will try to do the same.”
A spokeswoman for Mr Obama declined to comment on the incident, and referred reporters to the Secret Service statement.