Packages containing homemade explosive devices have been intercepted en route to the homes of former US presidents Barack Obama and Bill Clinton in a wave of apparent politically-motivated attacks.

New York Mayor Bill de Blasio on Thursday morning (AEST) confirmed a similar package had been sent to his offices, calling the attempted bombings of prominent politicians and public figures an “act of terror”.

CNN reported that a package intercepted in its mailroom was delivered by a courier and addressed to former CIA director John Brennan, an outspoken critic of President Donald Trump and frequent commentator on the network.

FBI Miami said a potential bomb was mailed to the Florida office of Democratic Congresswoman Debbie Wasserman-Schultz, while Californian Democratic Congresswoman Maxine Waters confirmed her Washington DC office was the target of a suspicious package.

CNN’s home at the The Time-Warner Centre in Manhattan was evacuated and nearby streets were cordoned off as bomb experts swept the building.

FBI Special Agent in Charge C. Bryan Paarmann said the intercepted devices appeared to have been crude pipe bombs and were taken away to be inspected. There were no injuries.

All the confirmed bombs appeared to come from the same person or persons, John Miller, the New York Police Department’s head of intelligence and counterterrorism, told reporters.

Five packages containing “potentially destructive devices” were mailed in manila envelopes with six Forever stamps and labeled with the Florida return address of “DEBBIE WASSERMAN SHULTZ” (sic), the FBI said in a statement.

The FBI said the packages were addressed to Mr Obama, Hillary Clinton, former attorney general Eric Holder, Mr Brennan and major Democratic donor George Soros.

Forever stamps can be pre-purchased and used at any time regardless of future postage price rises.

The FBI said five of the packages were identical in appearance. Photo: FBI

The FBI issued a statement warning there may be more targets of the bombs in other locations.

“We ask anyone who may have information to contact the FBI. Do not hesitate to call,” FBI Director Christopher Wray said.

“No piece of information is too small to help us in this investigation.”

The package sent to the home of former secretary of state Hillary Clinton and her husband Bill Clinton was intercepted outside their residence in Chappaqua, New York.

The package sent to Mr Obama was sent to his office in Washington, the Secret Service said.

The devices appeared to be pipe bombs, according to the FBI. Photo: CNN

“We will not allow these terrorist thugs to change the way we live our lives,” Mr de Blasio, a vocal critic of US President Donald Trump, said.

Mr Trump described the attempted bombings as a despicable act, calling for unity.

“I just want to tell you that in these times we have to unify, we have to come together and send one very clear, strong, unmistakable message that acts or threats of political violence of any kind have no place in the United States of America,” the President said.

Mr Trump said “the full weight of our government” is investigating the packages and will “bring those responsible for these despicable acts to justice”.

Mr de Blasio called on Mr Trump to bring down the rhetoric in public debate ahead of the US mid-term elections.

“For everyone’s sake, the President, the Senate, the Congress, the governors, bring down the rhetoric,” he said.

CNN president Jeff Zucker released a statement calling on the White House to cease its attacks on the media.

Statement from CNN Worldwide President Jeff Zucker: pic.twitter.com/OXyIT6oSLT

— CNN Communications (@CNNPR) October 24, 2018

Mr Brennan said in August that Mr Trump’s actions were “treasonous” and described him as “drunk on power.”

Former president Bill Clinton was at home when the package sent to his residence was found, according to news reports. Former secretary of state Hillary Clinton was campaigning in Florida.

The Secret Service said the packages were identified during routine mail screening procedures.

A suspected bomb was sent to the Clinton’s New York state home. Photo: Getty

Neither of the Clintons nor Obama were at risk of receiving the packages, the Secret Service said.

The Secret Service, along with New York and Washington law enforcement agencies, are investigating to determine who sent the packages.

Mr Clinton thanked the efforts of the secret service and law enforcement officers in a tweet.

Thank you to the @SecretService and all law enforcement agencies who responded to this week's incidents. They work tirelessly to keep our country and communities safe. I am forever grateful for their efforts.

— Bill Clinton (@BillClinton) October 24, 2018

Soros’ foundation on Tuesday linked the packages to “hateful rhetoric” dominating US politics.

The White House said Mr Trump would attend a planned political rally in support of embattled Republican Governor Scott Walker in Wisconsin later Thursday.

-with AAP