BOGOTA -- At least 16 people were injured when six home-made bombs went off inside trash cans in Bogota during a protest march by thousands of civil servants, police said Thursday.

The nearly simultaneous explosions occurred in residential neighborhoods near the German and Peruvian embassies, a branch of US Citibank and outside a McDonalds, Bogota police chief Rodolfo Palomino told reporters.

He said a passenger bus had also been set on fire Thursday near the El Dorado airport, and that so far there were no clues as to the culprits of the crimes.

He said the bombs injured 16 people, but that "nobody was seriously hurt."

"They were low-powered, home-made bombs that make lots of noise but little damage," another police spokesman told AFP.

United Workers Union leader Tarsicio Mora condemned the bombings, calling them "acts of terror that seek to undermine the social protest movement and peaceful demonstrations."

The bombs went off as thousands of civil servants on a 24-hour strike demonstrated in central Bogota in support a two-week-long protest by thousands of indigenous people in southern Colombia against President Alvaro Uribe's administration.

Their chief demand is that the government return ancestral land they deem was taken illegally from indigenous communities over the past 15 years.

Three Indians were killed by gunfire in clashes with police in southern Cauca department earlier this month, with the government disputing reports that riot police fired the fatal shots.