US Vice President Mike Pence has blasted "cowardly" attacks as a series of bombs were sent to prominent Democrats and a US news organisation, in an apparent act of terrorism.
The Secret Service said it had intercepted two bombs addressed to the homes of former president Barack Obama and 2016 presidential nominee Hillary Clinton.
The Florida office of Democratic congresswoman Debbie Wasserman Schultz was evacuated after police found a suspicious package addressed to Obama-era attorney general Eric Holder, local media reported. Wasserman Schultz was chair of the Democratic National Committee between 2011 and 2016.
Another package was sent to Time Warner's New York offices that host CNN, the channel reported.
CNN moved its stream to Washington DC as reporters were forced to evacuate their New York building during a live broadcast.
The package was addressed to former CIA director John Brennan – a contributor to NBC News and MSNBC – with a return address to Wasserman Schultz's office.
This is the suspicious package received this morning at the Time Warner Center, which houses the CNN New York bureau.
— CNN (@CNN) October 24, 2018
Officials told the New York Times that the devices were similar to the one sent to billionaire philanthropist George Soros on Monday.
The White House condemned the "attempted violent attacks" against Obama, the Clintons and other public figures in a statement, Reuters reported.
Potential bombs were discovered by the Secret Service during a routine screening of post addressed to Clinton in Westchester County, New York yesterday and Obama in Washington, DC this morning.
As someone whose family has directly been the victim of these mail threats I condemn whoever did this regardless of party or ideology. This crap has to stop and I hope they end up in jail for a long time. https://t.co/pajRgM4hYm
— Donald Trump Jr. (@DonaldJTrumpJr) October 24, 2018
"Both packages were intercepted prior to being delivered to their intended location. The protectees did not receive the packages nor were they at risk of receiving them," the Secret Service said.
"The Secret Service has initiated a full scope criminal investigation that will leverage all available federal, state, and local resources to determine the source of the packages and identify those responsible," a statement added.