In what could almost be a scene from a Bollywood action film, an 18-year-old girl leaps from the top of a building on to a huge sheet held by a cheering crowd on the street below.
Minutes later, a body slumped in a chair is lowered from another building as a group of about 500 people look on in stunned silence.
India's commercial capital, Mumbai, is preparing for war with Pakistan.
The nuclear-armed South Asian neighbours have massed a million troops on their border since a December attack on Parliament that India blames on Pakistan-based terrorists.
Fears of a war between the rivals - who have already fought three wars since their independence from Britain in 1947 - have grown since an attack on an army camp near Jammu in May that India again blamed on Pakistan-based terrorists.
Officials in Mumbai say the coastal city of 12 million is ready.
"The mock drill is a confidence building measure. It will train people to deal with a crisis situation," T Singaravel, director of civil defence in Maharashtra, told Reuters.
Authorities say Mumbai is highly vulnerable because it has an atomic energy plant and is the nation's financial nerve-centre.
Hour-long drills conducted by groups of khaki-clad volunteers across the city include lessons in evacuation, detecting nuclear radiation, first aid, rescuing people from fires and crisis communication with the police.
As part of the drill, some 250 sirens will wail across Mumbai at the same time on Monday to get people used to the sound of a loud alarm if war breaks out.
"So far, we have been testing sirens in low sound to avoid creating panic among people. But we feel they should know what a siren means and what precautions to take," Singaravel said.
While it may be business as usual across most of the metropolis where people still spend long hours drinking at pubs and watching soccer games on television, authorities are taking no chances.
The state plans to distribute pamphlets informing people about sirens, blackouts, underground water tanks used by fire fighters and warehouses that can serve as crisis shelters.
Singaravel said nearly 35,000 trained volunteers from the civil defence force had prepared a list of hospitals, doctors, pharmacies and possible shelters.
Authorities are also holding a 14-day civil defence course at centres across the city to train volunteers. Thousands of people have enrolled and many more are keen to sign up, Singaravel said.
At one class, about 60 students, including government and court officials, businessmen and students were taught the intricacies of nuclear weapons and the damage they could cause.
"I see a lot of hope in this. I may be of some help to people," said 75-year-old Sadashiv Dalvi, a retired sales officer, who had enrolled for the class.
"We had to increase the number of classes. Since May, there has been a big demand for this course," he said.
"Anybody undergoing this course can keep a cool head," Singaravel said.
More reports on the Indo-Pak standoff
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