Washington (CNN) Former Director of National Intelligence James Clapper said the threat posed by the dozen of suspicious packages sent to top Democrats and President Donald Trump's critics, including him, is not going to prevent them from speaking out against the Trump administration.

"I do want to just echo one thing that (former CIA Director) John Brennan said and that this is not going to silence the administration's critics," Clapper said during a phone interview on Friday with CNN's Poppy Harlow and Jim Sciutto.

The former intelligence chief told CNN he believes the 12 suspicious packages are "definitely domestic terrorism, no question in my mind."

Clapper warned that anyone who has in any way "publicly been a critic of President Trump, needs to be on an extra alert and take some precautions, particularly with respect to mail."

But he added later, "We can't stop our lives. We have to go on."

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