Drones hovered over the pandemic-stricken Indian city of Ahmedabad on Saturday spraying disinfectant on the streets, hours after security forces clashed with residents who flouted a toughened lockdown.

The western city of 5.5 million people has become a major concern for authorities as they battle a surge in coronavirus deaths and cases across India.

Ahmedabad accounts for 343 of the almost 2,000 deaths reported nationwide and just under ten percent of cases registered. Other cities in Gujarat state have also been badly hit.

Drones sprayed from the air while fire engines and other city vehicles toured the empty streets sending out clouds of cleaning agent onto roads and the outside of buildings.

“We have started a massive exercise to spray disinfectant in all zones of the city,” said the city’s acting chief administrator Rajiv Gupta.

India has been in the grip of the world’s biggest lockdown since March 25, which was made stricter 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.

Authorities have insisted the pandemic crisis is under control and have started to ease restrictions in many parts of India to let agriculture and some companies get back to work. Experts however have warned of an increasing toll despite the lockdown.

The virus is spreading particularly quickly in major cities such as Mumbai, New Delhi and Ahmedabad. And experts say the toll numbers are higher than reported because of the lack of testing and poor accounting for deaths.

While the number of deaths is low compared to the United States and the worst-hit European nations, health specialists say India’s pandemic curve may only peak in June and July.

Shamika Ravi, an economic advisor to the government who has become a much-followed commentator on the pandemic’s spread, said Saturday that the “infection is way ahead of our knowledge” in Gujarat and Maharashtra, which includes Mumbai, because there is not enough testing.