An explosion Thursday from a device tossed into a group of vendors at a market in Bangkok injured 15 people, two of them seriously, police said.

The incident occurred at the Klong Toey market in the Thai capital where vendors had gathered to protest against the new management company for the market, Thai News Agency reported.

TNA quoted a witness as saying he saw a man toss the explosive device from an overpass.

Hundreds of vendors have been demonstrating to oppose the award of the market concession to Legal Professional Co. by the Port Authority of Thailand, the report said.

The previous day, more than 10 men had visited the market area and fired several shots in the air to threaten the vendors, the Bangkok Post reported.