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Police in northern India have been using drones that fire pepper spray to control protesters.

The police in the city of Lucknow bought five drones each capable of carrying cameras and two kilos of pepper spray.

Their crowd control capabilities have been tested in winds and built-up areas.

“The results were brilliant,” said police chief Yashasvi Yadav, speaking to AFP.

"Pepper is non-lethal but very effective in mob control. We can spray from different heights to have maximum results," he said.

Pepper spray is a chemical that irritates the eyes, causing tears, pain and temporary blindness. It's used to disperse riots and deter attackers.

Following tests, the drones will be rolled out later this month.

The city has previously used unmanned aerial vehicles for surveillance purposes during busy religious festivals.

While the pepper spray might be lethal, having a heavy drone flying over a lot of people isn't necessarily a good idea - what happens if it suffers motor failure and falls from the sky?

In the UK the CAA says that drones can't be flown within 150 metres of a congested area or any open-air gathering of more than 1,000 people. Nor can they be flown within 50 metres of any vehicle or person who isn't flying the aircraft.

Having drones that fire pepper spray at people would, therefore, not be allowed in the UK.