HONG KONG - HONG KONG police were investigating on Sunday after dozens of Christmas shoppers were burned by bottles of acid hurled from a high-rise building on to one of the city's busiest streets, a report said.

Police said 46 people were injured in a deliberate attack as two large plastic bottles of liquid crashed to the ground in the teeming Mong Kok district at about 5pm on Saturday, the Sunday Morning Post reported.

Witnesses said the victims screamed out and rushed to find water to wash off the liquid, which burned holes in their clothes and damaged their skin, the report said.

'A bottle came down,' one man told the English-language paper. 'It looked like an ordinary bottle of water, and the crowd began to disperse. Then I saw people with red faces and eyes in pain.'

All 46 victims had been released from hospital by the end of Saturday, the report said.

Police said they searched the building where the bottles appeared to be thrown from, but had not arrested any suspects.

'Traces of caustic liquid were left on the ground,' police superintendent Annie Fonda told the newspaper.

'Judging by the traces and the positions of the two bottles, this is not an accident. We believe someone intentionally hurled them from a height.'