India's capital, Delhi, will begin randomised Covid tests at airports, bus stops and train stations amid what some experts say is a second wave.

Mumbai, a financial hub and virus hotspot, ordered mandatory testing in busy areas earlier this week.

Cases have surged in recent weeks - on Wednesday, India reported more than 47,000 new cases and 275 deaths, it's highest this year.

It has reported more than 11.7 million cases and 160,000 deaths so far

India's caseload dropped significantly at the start of this year - it reported under 10,000 new infections on some days. And this coincided with the launch of the country's vaccine drive, the largest in the world.

But March saw a sharp uptick, with more than 40,000 new infections reported daily since Sunday.

The surge in cases comes during what some experts have called a 'delicate phase' for India - the healthcare system is already exhausted from a year-long battle against the coronavirus.

Reasons for the rise in cases range from poor adherence to Covid-19 safety protocols and lax test and trace and isolation rules to new variants that are more infectious.

States are now re-introducing restrictions to stem the spread of the virus. Public gatherings and celebrations during Holi, a popular Hindu festival, have been barred.

Delhi has also designated cinema halls, the metro rail and religious places as potential "super spreader" areas. Local officials have been told to increase surveillance of in these places to make sure people are wearing masks and maintaining social distance.

The federal government has also extended its ban on international commercial flights until 30 April. Authorities said only those flying approved routes will continue to run.

Maharashtra, where Mumbai is located, accounts for nearly 70% of the national caseload. Some districts have already resorted to intermittent lockdowns and curfews. In Mumbai, officials said rapid tests will be done randomly in areas such as shopping centres and train stations.

Experts recommend scaling up vaccination alongside improving test and trace and safety protocols.

More than 50 million doses have been administered so far and the government has announced that from 1 April the drive will further expand to include anyone above the age of 45. It hopes to vaccinate some 250 million people by the end of July.

So far, more than 48 million people have received atleast one dose of a coronavirus vaccine in what is the world's biggest inoculation drive. However the pace of vaccinations will have to pick up if the government intends to cover 250 million people by the end of July. Experts say unless the drive is scaled up, India could miss its target.

On Tuesday, the Ministry of Home Affairs issued fresh guidelines stressing increased testing and adherence to "Covid-appropriate behaviour."

"Keeping in view a fresh surge in COVID-19 cases, which is being witnessed in some parts of the country, the guidelines mandate the State/ UT Governments to strictly enforce the Test- Track-Treat protocol in all parts of the country; ensure observance of COVID appropriate behaviour by everyone; and, to scale up the vaccination drive, to cover all the target groups." the ministry said in a statement.