Thousands of dead fish have washed up on the banks of a polluted lake in India's southern technology hub of Bangalore.

V. Purushottam, president of a residents' group, says people spotted the dead fish floating in Ulsoor Lake on Monday in a residential district.

Purshottam says sewage from many parts of the city has been flowing into the lake, depleting oxygen levels in the water.

Kiran Kumar, an environmentalist, says water samples are being collected for testing.

Purshottam says authorities have ignored pleas to repair a barrier that is supposed to keep sewage from flowing into the lake.

India has some of the world's most polluted air. More than half of its 1.2 billion people still defecate in the open, causing rivers and lakes to stink with sewage.