President Donald Trump has called on the media "to stop the endless hostility", after suspected explosives were posted to high-profile US figures.
He was speaking after parcels were sent to CNN and top Democrats, including Barack Obama and Hillary Clinton.
None of the packages exploded. The FBI has launched a hunt for their sender.
The president's critics called his comments hypocritical, as he often uses vicious language against his opponents and the press.
In scripted remarks at a Wednesday night rally in Wisconsin, the president vowed to catch the perpetrator, while calling on the media to end "constant negative and oftentimes false attacks and stories".
Mr Trump also called for more civility in public life, saying: "Those engaged in the political arena must stop treating political opponents as being morally defective.
"No one should carelessly compare political opponents to historic villains, which is done often."
However, the president made no specific reference to the intended recipients of the packages.
Earlier CNN worldwide president Jeff Zucker criticised President Trump and the White House press secretary for not understanding that "words matter".
"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.
Who were the packages sent to?
Suspected bombs were sent to locations in New York, the Washington DC area and Florida, authorities said on Wednesday.
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
- California Democratic Congresswoman Maxine Waters
- Liberal philanthropist and financier George Soros (on Monday)
CNN's New York office was evacuated on Wednesday morning after the package, addressed to Mr Brennan, was found in its mailroom.
Another package, believed to have been addressed to former Vice-President Joe Biden, is being sought by US federal investigators.
Why is this so political?
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, which includes deriding media reports as "fake news" and calling his media critics "enemies of the people".
In August he called "the fake news media" the "opposition party".
THE FAKE NEWS MEDIA IS THE OPPOSITION PARTY. It is very bad for our Great Country....BUT WE ARE WINNING!— Donald J. Trump (@realDonaldTrump) August 16, 2018
Some of Mr Trump's supporters have said they believe the packages sent this week 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 mid-terms, with US politics highly polarised.
What has the reaction been?
New York City Mayor Bill de Blasio called the attempted attacks "an act of terror".
He told 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."
On Wednesday, White House spokeswoman Sarah Sanders condemned the "attempted violent attacks" against the public figures. She specified in a follow-up tweet that the White House also condemned threats made to CNN.
The president's verbal assaults on the media have repeatedly raised concern, including from UN experts who said they undermine press freedom and raise the risk of violence against journalists.
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 said the president's latest words "ring hollow until he reverses his statements that condone acts of violence".
The FBI has said its ongoing investigation is "of the highest priority".
What was in the packages?
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.
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.