Thousands of people demonstrated Saturday in 100 U.S. cities demanding justice in the case of slain black teenager Trayvon Martin, with the participation of the dead boy's parents and celebrities like singers Beyonce and Jay-Z.

The "Justice for Trayvon" campaign, organized by the National Action Network, rallied demonstrators across the country, from Los Angeles to Washington to New York, to protest the jury's decision to acquit neighborhood watch volunteer George Zimmerman for Martin's death.

The center of attention in New York were Jay-Z and Beyonce, who were photographed with the Rev. Al Sharpton and with Trayvon's mother, Sybrina Fulton.

"God is healing my heart this very moment. But as I watch so many people come together, he reminds me that we have a lot of work to do," Fulton wrote on her Twitter account at the beginning of the demonstration.

Protesters asked the U.S. Justice Department to open an investigation into the case following Zimmerman's acquittal. The government agency is considering opening a civil rights suit against the suspect, who maintains that he shot Martin in self-defense.

The rally in Miami gathered some 500 people including the teen's father, Tracy Martin, while hundreds came together in Washington, with similar crowds showing up to protest in front of federal courts in Atlanta, Chicago and Los Angeles.

"As a community, we need to come together and we need to support justice for Trayvon...we need to do it in a peaceful manner," Donna Wade, one of the protesters in Los Angeles, said on the CNN television network.

The demonstrations came a day after U.S. President Barack Obama got into the debate about Martin with a very personal speech that underscored the racist background of the case.

"Trayvon Martin could've been me 35 years ago," Obama said after making a surprise appearance before reporters in the White House briefing room. EFE