Police in the southern Indian state of Karnataka have used tear gas to disperse farmers angry at having to share water with neighbouring Tamil Nadu.

Officers have made more than 600 arrests since the state government complied with a court order to release disputed river water on Sunday night.

Officials say two billion cubic feet of water from the River Cauvery has been released so far - water, the farmers say, they need to irrigate their crops.

Hundreds of policemen in riot gear have been deployed at the four main Cauvery reservoirs in the region to prevent angry farmers from storming the dams.

The farmers say sharing the water will affect them most, and have been erecting roadblocks in parts of the state in protest.

Police said over 1,500 farmers had brought traffic to a standstill on the highway linking the state capital, Bangalore, with the city of Mysore.

All schools and colleges in the state have been closed until Wednesday as a security precaution.

The authorities also said they have suspended all trains passing through the region for two days.

Crisis meeting

Authorities in Karnataka decided to release the water late on Sunday.

The cabinet meeting came hours before a crucial hearing in the Supreme Court on Monday to adjudicate on a petition filed by Tamil Nadu against its neighbour.

Karnataka Chief Minister SM Krishna had been criticised for refusing to comply with a court order to release water from the Cauvery.

Last week, three judges in the Supreme Court said Karnataka was in contempt of court for deliberately disregarding the ruling.

Mr Krishna staged a march through Karnataka earlier this month to gather public support for his stand, after farmers protested against sharing water from the Cauvery reservoirs.

The bitter dispute over sharing the waters of the Cauvery, which flows through both states, has gone on for many years.