A 56-year-old man has been arrested in Florida in connection with a mail-bombing campaign aimed at critics of US President Donald Trump.
US officials named the man as Cesar Sayoc. He faces five charges including mailing explosives and threatening ex-presidents.
Mr Trump said the acts were “despicable and have no place in our country”.
Fourteen items have been sent in recent days to figures including ex-President Barack Obama and actor Robert de Niro.
Two were found in Florida and New York City on Friday morning.
Later, two more were discovered in California. Billionaire and Democrat donor Tom Steyer said that a package sent to him had been intercepted at a mail facility in Burlingame, and another addressed to Democrat Senator Kamala Harris was reported in Sacramento.
The incidents come less than two weeks before the US mid-term elections, with politics highly polarised.
The president praised law enforcement for the quick arrest of the suspect, describing the search as looking for a “needle in a haystack”.
“These terrorising acts are despicable and have no place in our country,” he said.
The comments were in stark contrast to Mr Trump’s tweet earlier in the day, when he suggested the incidents, which he described as “‘Bomb’ stuff”, were slowing Republican “momentum” in early voting.
But Mr Trump returned to the theme later, accusing US media of exploiting the latest case.
“The media’s constant, unfair coverage, deep hostility and negative attacks… only serve to drive people apart and to undermine healthy debate,” he said at a rally in North Carolina.
“We have seen an effort by the media in recent hours to use the sinister actions of one individual to score political points against me and the Republican party.”
US media reports suggest Mr Sayoc is a registered Republican who attended some of Mr Trump’s rallies in 2016 and 2017. However, the president rejected any suggestion that his rhetoric had contributed to the attacks.
“I heard he was a person that preferred me over others. There’s no blame, there’s no anything,” Mr Trump said.
Former intelligence chief James Clapper, one of the recipients of Friday’s packages, told CNN: “This is definitely domestic terrorism, no question in my mind.”
He said that anyone who had been a critic of President Trump needed to be on the alert and take extra precautions.
“I’m not suggesting a direct cause-and-effect relationship between anything he’s said or done and the distribution of these explosives. But I do think he bears some responsibility for the coarseness of civility of the dialogue in this country,” he added.
FBI Director Christopher Wray revealed that Sayoc was detained after his fingerprint was allegedly found on one of the packages.
Officials also said DNA and mobile phone data were used to track the suspect down. (Excerpts from BBC)