At least 20 people were arrested as pro-Trump demonstrators and counterprotesters gathered in the nation's capital on Saturday.

The majority were arrested for minor incidents. However, late in the day, as the crowds thinned and the scene got more violent, police said one protester was stabbed multiple times. Seven guns were confiscated during the day's events as well, police said.

The Metropolitan Police Department did not release the charges for all 20 people, but said earlier in the day that four people were arrested for firearms violations, two were arrested for simple assault, two were arrested for disorderly conduct, one person was arrested for not having a permit and one was arrested for assault on a police officer.

Two police officers were also injured.

The Metropolitan Police Department announced the arrests just before 10 p.m., but said a full report of those arrested would be released on Sunday.

Police had warned those set to gather for the event that open carry of firearms is illegal in Washington, D.C. Authorities were hoping to stem the tradition of some so-called militia groups who have shown up to protests around the nation openly displaying weapons.

The large groups marching in Washington during the daylight hours were largely peaceful.

ABC News' Ben Siu and Will Gretsky contributed to this report.

A small crowd of Trump supporters have gathered outside the Trump National Golf Club in Virginia, according to a pool report.

About 30 supporters were on the sidewalk outside the club Saturday afternoon, waving flags and banners, the report said. One person had a handwritten "Stop the steal" sign."

Trump was seen arriving at the golf club earlier on Saturday, where he was met by protesters rallying against him.

One week after addressing the nation for the first time as president-elect from Wilmington, Delaware, Joe Biden has penned an open letter to his home state published by the Delaware News Journal, thanking its denizens for helping him get to the Oval Office after nearly 50 years in public life.

“This election was won by bringing Americans from all walks of life together. It was won because of the hard work and faith of so many people across this country. It was won with a promise to restore the soul of this nation and build back better than ever. However, we never could have done it without you -- without Delaware,” Biden wrote in the letter, which the publication said it asked him to write.

As he often did on the trail, Biden spoke about the values he learned growing up, and the president-elect offered the same unity pitch he delivered last week.

“Our country has never needed the values I learned here in Delaware more. That’s why, although I am a proud Democrat, I promise you, I will be an American President, and work as hard for those who didn’t vote for me, as those who did,” he said.

-ABC News' Molly Nagle

As pro-Trump protesters gathered in Washington, D.C., on Saturday, President-elect Biden and his wife, Jill Biden, went out for a bike ride in Delaware's Cape Henlopen State Park. 

On Thursday, Biden traveled from Wilmington to Rehoboth Beach, Delaware, where the Bidens own a vacation home and where he has continued meeting with transition advisers, according to the Biden campaign.

Meanwhile, Trump was seen arriving at Trump National Golf Club in Virginia, met by protesters rallying against him.