St. Louis, August 15 (RHC)-- Thousands of protesters have held demonstrations in more than 100 cities across the United States to honor the memory of a Black teenager shot dead by a white policeman in Missouri.

The protests have been held in the St. Louis suburb of Ferguson, Missouri, every night since 18-year-old Michael Brown was shot multiple times and killed by police on Saturday. Police have dealt with the demonstrators harshly, using tear-gas and the tactics of mass arrests.

On Thursday, huge demonstrations were staged in Washington, New York, Boston, St. Louis and Philadelphia, NBC News reported. Protesters criticized the police for killing the unarmed Brown and called for an end to the racial killings.

Meanwhile, the security of the city of Ferguson, where the deadly happened, has been handed over to state police. The decision has been taken after nights of violent clashes there. Local police have been criticized for dealing harshly with protesters.

Earlier in the day, U.S. President Barack Obama called for "peace and calm" and urged police to respect protesters. He also demanded an investigation into the killing.