Washington  - The volunteer at the shelter for homeless teens pushed up his sleeves and took up a roller of blue paint.

"This is good practice cause I'm moving to a new house tomorrow," he joked in playful banter with his fellow volunteers.

But this was no ordinary do-gooder. This was Barack Obama, who will move into the White House Tuesday as the 44th president of the United States.

Monday was Martin Luther King Jr Day, and Obama urged Americans to engage in community service as they remembered the civil rights movement leader and looked forward to the first African American president.

Several hundred volunteers took up that call at an event to feed the homeless outside Washington's main public library, which is named for the slain leader.

More than 5,000 volunteer groups had helped organize 11,000 similar projects nationwide, involving as many as 1 million people across the country, Obama said.

About 600 volunteers were expected throughout the day outside the Martin Luther King Jr Memorial Library, where a long line of young, primarily African American volunteers scooped up heaping portions of mashed potatoes, green beans and meat for the city's homeless. The hungry came from nearby neighbourhoods and five of the city's largest homeless shelters.

It was the 22nd year for the event called We Feed Our People, but Dy Brown from the mayor's office on volunteerism said interest this year was unprecedented leading to a larger than normal effort.

Despite its serious purpose, the event took on a party atmosphere. Organizers had cordoned off a city block and musicians Josh Groban and Herbie Hancock serenaded a crowd of out-of-town visitors and office workers, urging them to make donations to a local food bank. They were joined by Martin Luther King III, the civil rights leader's son, who urged the crowd to continue his father's legacy of service.

"We cannot go home on Wednesday and think our job is done," King said of the day after the inauguration. "On Wednesday, we've got to roll up our sleeves."

Nearby, women collected canned foods and university students distributed clothing to the homeless.

"We appreciate that (Obama) was making Martin Luther King Day more than just a day off school," said Kimberly Clincy, 20, a student at the historically black Howard University in Washington.

Volunteers, including members of black fraternities and sororities, mingled alongside homeless men and women carrying trash bags of donated clothes and dozens of street vendors hawking Obama souvenirs.

Many of those who came to help were from out of town and simply wanted to be part of the entire inaugural experience, including Obama's call to service.

"Finally, we have someone who really does care about the people, and it makes you want to serve," said Sanaa Msemagi, a native Californian who was collecting canned goods outside the library. (dpa)