Indian authorities used drones and fire engines to disinfect the pandemic-hit city of Ahmedabad on Saturday, as virus cases surged and police clashed with migrant workers protesting against a reinforced lockdown.

The western city of 5.5 million people in Prime Minister Narendra Modi's home state has become a major concern for authorities as they battle an uptick in coronavirus deaths and cases across India.

Ahmedabad accounts for 343 of the almost 2,000 deaths reported nationwide and almost 10 percent of India's cases. Other cities in Gujarat have also been badly hit.

Locals watched from their balconies as drones sprayed disinfectant from the air while fire engines and other vehicles toured the empty streets sending out clouds of cleaning agent.

"All zones" of the city would be disinfected, according to acting chief administrator Rajiv Gupta.

India has been in the grip of the world's biggest lockdown since March 25, which was tightened in Ahmedabad on Friday because of the accelerated spread of the virus. Hundreds of paramilitaries kept people off the streets and virtually all stores have been closed for at least a week.

On Friday night, security forces fired tear gas at stone-throwing residents who ventured out. At least 15 people were arrested and the police presence was stepped up Saturday.

Fresh clashes erupted Saturday between about 500 migrant workers and police in Gujarat's industrial hub of Surat.