Vermont Senator Bernie Sanders has warned Republicans against skipping their town halls and said that they must "have the guts" to take tough questions.

"If you don't have the guts to face your constituents, then you shouldn't be in the United States Congress," the former presidential candidate told CNN.

More than 200 GOP lawmakers have skipped town halls in their home states during the first recess amid a wave of voter anger over healthcare, jobs and President Donald Trump’s alleged ties to Russia and conflicts of interest.

"And if you need police at the meetings, that's fine, have police at the meetings, have security at the meetings," continued Mr Sanders.

"But don't use that as an excuse to run away from your constituents after you support repealing the Affordable Care Act, throwing 20 million people off of health insurance, doing away with preexisting conditions.

"If you are going to do all those things, answer the questions that your constituents have."

Senate Majority Leader Mitch McConnell, Arkansas Senator Tom Cotton, Tennessee Congresswoman Marsha Blackburn and Utah Representative Jason Chaffetz were some of those who were booed, jeered and shouted down at their town halls.

They also faced hundreds if not thousands of protesters outside the venue who were not admitted into the events.

Mr Trump claimed the protests were being organised by "thugs" and "liberal activists".

His press secretary, Sean Spicer, acknowledged that some people were "clearly upset" but did not understand why, as he insisted Mr Trump’s new healthcare plan should send a signal to voters that "help was on the way".

He added the protests had a "bit of professional, manufactured base in there".

For the first two months of the new Congress, only 88 in-person events with Republicans were organised. There are 292 Republicans in Congress.

Mitch McConnell's face drops as voter confronts him about jobs and healthcare