By Curtis Skinner

SAN FRANCISCO (Reuters) - Thousands of people took to the streets in U.S. cities on Friday to denounce the fatal police shootings of two black men this week, marching the day after a gunman killed five police officers watching over a similar demonstration in Dallas.

Protesters clogged roadways in New York City, Atlanta and Philadelphia on Friday evening, and events also were planned for San Francisco and Phoenix. Local media reports did not indicate any immediate instances of major clashes or injuries.

About 6 protesters arrested for blocking the street in front of the #Ferguson PD. pic.twitter.com/97mPyAnp2x — Robert Cohen (@kodacohen) July 9, 2016

Over 5,000 people are currently marching down the streets of Atlanta. Here's a video from an hour ago. #ATLisReady pic.twitter.com/fHRTekh0V5 — Everything Georgia (@GAFollowers) July 9, 2016

Atlanta's mayor in the middle of the protesters. @wsbtv pic.twitter.com/oWR2hxbfBZ — Erica Byfield (@EricaByfieldWSB) July 9, 2016

Thousands marched in Atlanta in what appeared to be the largest demonstration, chanting and waving signs demanding justice, video posted to social media showed. Footage from local broadcasters showed the massive crowd facing off with dozens of police vehicles that were stopped on a local interstate highway.

Eduardo Munoz/Reuters People take part in a protest against the killing of Alton Sterling, Philando Castile and in support of Black Lives Matter during a march along Manhattan's streets in New York July 8, 2016.

Eduardo Munoz/Reuters People walk over the names of people killed by police as they take part in a protest against the killing of Alton Sterling, Philando Castile and in support of Black Lives Matter during a march along Manhattan's streets in New York July 8, 2016.

Eduardo Munoz/Reuters People take part in a protest against the killing of Alton Sterling, Philando Castile and in support of Black Lives Matter during a march along Manhattan's streets in New York July 8, 2016.

Eduardo Munoz/Reuters People take part in a protest against the killing of Alton Sterling, Philando Castile, and in support of Black Lives Matter during a march along Manhattan's streets in New York July 8, 2016.

Joshua Roberts/Reuters Demonstrators with Black Lives Matter rally during a protest in front of the White House in Washington, U.S., July 8, 2016.

Joshua Roberts/Reuters Demonstrators with Black Lives Matter march during a protest in Washington, U.S., July 8, 2016.

Joshua Roberts/Reuters A demonstrator with Black Lives Matter holds up a sign during a protest in front of the White House in Washington, U.S., July 8, 2016.

Joshua Roberts/Reuters A Metropolitan police officer blocks traffic for Black Lives Matter protesters during a rally in Washington, U.S., July 8, 2016.

Joshua Roberts/Reuters Demonstrators with Black Lives Matter march during a protest at the Department of Justice in Washington, U.S., July 8, 2016.

Mark Wallheiser/Getty Images Magnolia Clark, right, 11 years-old and her mother Sarah Davis participate in a die-in at the New Orleans Police Department in New Orleans, Louisiana on July 8, 2016.

Mark Wallheiser/Getty Images Fifty New Orleans residents participated in a die-in at the New Orleans Police Department in New Orleans, Louisiana on July 8, 2016.

Shannon Stapleton/Reuters Dajia Dominguez,14, from Dallas, stands with her fist up at Rosa Parks Plaza near the shooting scene in Dallas, Texas, U.S., July 8, 2016.

Atlanta Mayor Kasim Reed tweeted that the rally was largely peaceful, though about 10 people had been arrested.

Friday was the second day of widespread demonstrations against use of force by police in the wake of the fatal shootings of 32-year-old Philando Castile near St. Paul, Minnesota and 37-year-old Alton Sterling in Baton Rouge, Louisiana.

Eduardo Munoz / Reuters People take part in a protest against the killing of Alton Sterling, Philando Castile and in support of Black Lives Matter during a march along Manhattan's streets in New York July 8, 2016.

Riot police with badge # covered push protestors out of intersection, corral remaining willing to risk arrest. pic.twitter.com/NOwK6JGZy2 — Noelle Evans (@KnowelleEvs) July 9, 2016

Castile was killed by police during a traffic stop late on Wednesday, and his girlfriend posted live video on the Internet of the bloody scene minutes afterward.

Sterling was killed during an altercation outside a convenience store with two white police officers. Graphic video of that incident caused an outcry on social media.

The two shootings stoked racial tensions that have flared repeatedly across the country following the 2014 killing of Michael Brown, an unarmed black teen, by a white police officer in Ferguson, Missouri.

Mark Wallheiser via Getty Images Protesters face off with Baton Rouge police in riot gear across the street from the police department on July 8, 2016 in Baton Rouge, Louisiana.

Thursday’s demonstrations were largely peaceful until gunfire erupted at a Dallas rally that was winding down.

Authorities said 25-year-old Micah Johnson, a black U.S. military veteran of the Afghan war who said he wanted to “kill white people,” launched a sniper attack that killed five police officers and wounded nine other people.

Police killed the gunman with a bomb-carrying robot after cornering him in a parking garage, ending an hours-long standoff.

(Editing by Colleen Jenkins and Mary Milliken)