Several thousand protesters marched Saturday from the White House to the Capitol to demand an end to the Iraq war, and at least 160 people were arrested when they jumped a barricade at the foot of the Capitol steps.

Many of the protesters were arrested without a struggle after they jumped over the waist-high barricade. But some grew angry as police attempted to push them back using large shields. At least two people were showered with chemical spray. Protesters responded by throwing signs and chanting: "Shame on you."

The arrests came after protesters initially decided to lay down on the Capitol lawn with signs on top of their bodies to represent soldiers killed in Iraq. When police took no action, some of the protesters decided to start climbing over the barricade.

Before arriving at the Capitol lawn, the demonstrators marched on Pennsylvania Avenue holding banners and signs and saying, "What do we want? Troops out. When do we want it? Now."

Counterprotesters lined the sidewalks behind metal barricades. There were some heated shouting matches between the two sides.

The protesters gathered earlier Saturday near the White House in Lafayette Park with signs saying "End the war now" and calling for President Bush's impeachment. The rally was organized by the ANSWER Coalition and other groups.

Organizers estimated that more than 100,000 people attended the rally and march. That number could not be confirmed; police did not give their own estimate. But there appeared to be tens of thousands of people in attendance, and the march stretched along multiple blocks of Pennsylvania Avenue.

Anti-war activist Cindy Sheehan told the crowd is was time to be assertive.

"It's time to lay our bodies on the line and say we've had enough," she said. "It's time to shut this city down."

Army veteran Justin Cliburn, 25, of Lawton, Okla., was among a contingent of Iraq veterans in attendance.

"We're occupying a people who do not want us there," Cliburn said of Iraq. "We're here to show that it isn't just a bunch of old hippies from the 60s who are against this war."

About 13 blocks away, nearly 1,000 counterprotesters gathered near the Washington Monument, frequently erupting in chants of "U-S-A" and waving American flags.

Retired Air Force Lt. Col. Robert "Buzz" Patterson, speaking from a stage to crowds clad in camouflage, American flag bandanas and Harley Davidson jackets, said he wanted to send three messages.

"Congress, quit playing games with our troops. Terrorists, we will find you and kill you," he said. "And to our troops, we're here for you, and we support you."