Four police officers delivered graphic, riveting testimony Tuesday about their violent clashes with rioters while defending the US Capitol on January 6, as a congressional panel launched its probe of the deadly insurrection.

Defying several Republicans openly opposed to scrutinizing the attack blamed on supporters of former president Donald Trump, the witnesses described being punched, kicked, pepper sprayed, threatened with death and branded traitors by a rampaging mob intent on blocking certification of Joe Biden's election victory.

It was "something from a medieval battle," Capitol Police Sergeant Aquilino Gonell, an immigrant US Army Iraq combat veteran, told the panel, as he wiped away tears.

US Speaker of the House Nancy Pelosi, a Democrat, led the successful push for impeachment of President Donald Trump, but all eyes are on the Senate's top Republican Mitch McConnell over whether he votes to convict the president
US Speaker of the House Nancy Pelosi, a Democrat, led the successful push for impeachment of President Donald Trump, but all eyes are on the Senate's top Republican Mitch McConnell over whether he votes to convict the president AFP / Brendan SMIALOWSKI

"I recall thinking to myself, this is how I'm going to die, defending this entrance," said Gonell, who expressed shock and anger at continuing efforts to "whitewash the facts."

Metropolitan Police Department officer Daniel Hodges described how "terrorists pushed through the line and engaged us in hand-to-hand combat," with at least one rioter trying to gouge out the policeman's eyes.

The gripping accounts served as opening testimony in a landmark first hearing of the House Select Committee to Investigate the January 6th Attack, which opened with hair-raising videos of the deadly rampage.

But it was the three-plus hours of emotional, often brutal accounts of officers under siege that set the tone for a probe expected to last several months.

Congress staffers barricade themselves after Trump supporters stormed inside the US Capitol in Washington, DC on January 6, 2021
Congress staffers barricade themselves after Trump supporters stormed inside the US Capitol in Washington, DC on January 6, 2021 AFP / Olivier DOULIERY

Half a year after hundreds of Trump supporters conducted the worst assault on the Capitol in two centuries, more than 535 arrests related to the riot have been made, according to officials.

But the work of the committee has become a political flashpoint.

Conspiracy theories have swirled. Some Republican lawmakers insist January 6 was a peaceful demonstration and endorse Trump's baseless claim that the election was rigged.

With such false narratives gaining traction, committee members framed their investigative mission as an appeal for truth.

Supporters of US President Donald Trump protest outside the Philadelphia Convention Center
Supporters of US President Donald Trump protest outside the Philadelphia Convention Center AFP / Kena Betancur

"We know there is evidence of a coordinated planned attack," the panel's Democratic chairman Bennie Thompson told the hearing.

"We know that the men and women who stormed the Capitol wanted to derail the peaceful transfer of power in this country."

Thompson vowed the committee would be "guided solely by the facts," adding "there's no place for politics or partisanship in this investigation."

US House Minority Leader Kevin McCarthy is opposed to the select committee investigating the mob attack
US House Minority Leader Kevin McCarthy is opposed to the select committee investigating the mob attack AFP / SAUL LOEB

Rioters, fueled by an aggressive Trump rally in Washington that day, fought their way into the Capitol, hunted for House Speaker Nancy Pelosi, chanted "Hang Mike Pence!" and sought to block certification of Biden's November presidential election victory.

US Capitol Police officer Harry Dunn recalled the racial epithets including the N-word hurled at him by rioters, many of whom were associated with ultra-nationalist and white supremacist groups.

Washington police officer Michael Fanone, who was beaten by rioters, is among the first people to testify before a congressional select committee
Washington police officer Michael Fanone, who was beaten by rioters, is among the first people to testify before a congressional select committee GETTY IMAGES NORTH AMERICA / WIN MCNAMEE

Metropolitan Police Department officer Michael Fanone said he was called "traitor" by rioters, who beat and tasered him unconscious.

"Nowhere in my wildest imagination did I ever expect to be in that situation," said Fanone, who suffered a heart attack during the insurrection.

"The indifference shown to my colleagues is disgraceful!" Fanone seethed.

The fiery remark appeared aimed at Republican lawmakers who have boycotted the committee and downplayed January 6 -- but it also touched on the building's glaring security deficiencies.

Five people died during or shortly after the insurrection, plus two policemen who later died by suicide. More than 100 officers were injured.

Trump has dismissed the probe as "fake and highly partisan" and attempted to blame Pelosi for allegedly failing to protect the Capitol, accusations echoed by his Republican backers.

Pelosi hit back, with her office declaring Republicans are peddling in "deflection, distortion and disinformation."

And officer Gonell, asked about Trump describing the rioters as a loving crowd, castigated the former president for having "egged them to continue fighting."

Pelosi and others had wanted a bipartisan, independent commission to investigate the riot and its origins. Even House Minority Leader Kevin McCarthy in January voiced support.

But with Republicans increasingly concerned that a probe could prove politically damaging for their party, they opposed a deep dive.

House Republican leadership pulled its five committee appointments last week after Pelosi rejected two of McCarthy's picks.

To avoid an all-Democrat panel, Pelosi named two Republicans: Trump critics Liz Cheney and Adam Kinzinger.

"No member of Congress should now attempt to defend the indefensible, obstruct this investigation, or whitewash what happened that day," Cheney told the hearing.

She also is seeking a full accounting of what the Trump administration might have known in advance, stressing she wants all White House communications from that day investigated.

Kinzinger made an emotional appeal to fellow Republicans.

"Many in my party have treated this as just another partisan fight. It's toxic" and should stop, he said.

Congress soon heads into a lengthy recess. Thompson signalled new hearings could be held during the break and committee members expressed eagerness to subpoena documents and more witnesses.