Six members of the Oath Keepers militia group were convicted Monday on charges of joining the January 6, 2021 US Capitol attack by supporters of president Donald Trump, local media reported.

In the third trial focused on the Oath Keepers, seen as central to planning and carrying out the violent insurrection, four members were found guilty of conspiracy to disrupt Congress, which can bring 20 years in prison.

Two others were convicted on lesser charges, CBS News and others reported.

The conviction came as Trump himself is under increasing threat by prosecutors investigating election wrongdoing in Washington and Georgia, and could be charged this week in New York for illicit hush money payments.

The six found guilty Monday included Sandra Parker, a retired Ohio woman in her 60s who donned camouflage combat gear to join the coordinated push by the group to force their way into the Capitol as legislators prepared to confirm Trump rival Joe Biden as the next president.

It also included Connie Meggs, who joined the attack with her husband Kelly Meggs, the head of the Florida chapter of the Oath Keepers.

Monday's convictions were for the third group of Oath Keepers charged in the January 6 litigation.

While most of the nearly 1,000 people accused of taking part have faced lesser charges like illegal entry, some of the heftiest charges like sedition and conspiracy have been reserved for the Oath keepers and fellow militia Proud Boys.

In November Kelly Meggs and Oath Keepers founder Stewart Rhodes were found guilty of sedition.

In January four others were found guilty of sedition and conspiracy, fortifying the government's argument that the January 6 attack was not simply spontaneous actions by fervid Trump-backers, but that there was significant planning and coordination involved.

Monday also marked the halfway point in the trial of five members of the far-right Proud Boys, who allegedly worked in parallel with Oath Keepers to organize some of the January 6 violence.

Their convictions could raise the odds that Trump himself and people around him who supported his effort to overturn Biden's election victory could face equally serious charges like a conspiracy for allegedly encouraging the violence.

Trump is under investigation by a Justice Department special counsel for his role in January 6. Three weeks before the violence, he urged his supporters to descend on Washington, tweeting "Be there, will be wild."

He is also facing possible indictment in Georgia for allegedly pressuring local officials to change the election results.

And he could be charged as soon as this week in New York in a hush-money case related to the 2016 election.