Experts have raised concerns over India's emergency approval of a locally-produced coronavirus vaccine before the completion of trials.

On Sunday, Delhi approved the vaccine - known as Covaxin - as well as the global AstraZeneca Oxford jab, which is also being manufactured in India.

Prime Minister Narendra Modi touted the approval as a "game changer" but health experts warn it was rushed.

Health watchdog All India Drug Action Network said it was "shocked".

It said that there were "intense concerns arising from the absence of the efficacy data" as well a lack of transparency that would "raise more questions than answers and likely will not reinforce faith in our scientific decision making bodies".

The statement came after India's Drugs Controller General, VG Somani, insisted Covaxin was "safe and provides a robust immune response".

He added the vaccines had been approved for restricted use in "public interest as an abundant precaution, in clinical trial mode, to have more options for vaccinations, especially in case of infection by mutant strains".

"The vaccines are 100% safe," he said, adding that side effects such as "mild fever, pain and allergy are common for every vaccine".

The All India Drug Action Network, however, said it was "baffled to understand the scientific logic" to approve "an incompletely studied vaccine".

One of India's most eminent medical experts, Dr Gagandeep Kang, told the Times of India newspaper that she had "not seen anything like this before". She added that "there is absolutely no efficacy data that has been presented or published".

Even social media users were quick to point out that approving the vaccine before trials were complete was a matter of concern irrespective of how safe or effective the vaccine eventually turned out to be.

A matter of trust
Vikas Pandey, BBC News, Delhi

Many scientists and opposition politicians have raised questions over what they say is the hasty authorisation of Covaxin, an Indian-made vaccine by local pharmaceutical firm Bharat Biotech.

The company has developed the vaccine with the state-run Indian Council of Medical Research - and the effort has been touted as an example of India's might in vaccine development and production.

Regulators say the vaccine is safe and effective. The firm says phase 1 and phase 2 trials have shown good results.

But scientists say that the government's decision not to release data on the vaccine's efficacy for peer review has raised concerns.

Mr Modi has welcomed the approval, saying Covaxin is a shining example of his ambitious Atmnirbhar (self-reliance) India campaign.

But experts worry that questions over the approval process don't bode well for the campaign. And there could be deeper issues. Many believe that the government needs to be more transparent about the authorisation process because the success of the Covid-19 vaccine programme depends on public trust.

The emergency authorisation also sparked a fierce debate on Indian Twitter on Sunday night between ministers and opposition leaders.

India's health minister Dr Harsh Vardhan called out opposition leaders for failing to "applaud" the country's "prowess" in locally producing a vaccine.

Members of the main opposition Congress party, Shashi Tharoor and Jairam Ramesh, and former chief minister of Uttar Pradesh state, Akhilesh Yadav, were among those who raised concerns about the manner in which Covaxin was approved.

The approval comes as India gears up to vaccinate its population of more than 1.3 billon people. Amid fears that richer countries are buying up much of the vaccine supply, India too appears to be stockpiling vaccines.

In an interview with the Associated Press, Adar Poonawalla, whose Serum Institute of India (SII) is manufacturing the AstraZeneca Oxford vaccine, said the jab was given emergency authorisation on the condition that it would not be exported outside India.

Mr Poonawalla said his company, the world's largest vaccine maker, was also not allowed to sell the shot in the private market.

This has raised concerns in India's neighbouring countries, including Nepal and Bangladesh, which were primarily depending on the SII to start vaccinating their populations.

Bangladesh had already ordered 30 million doses of the vaccine in the first phase, Reuters reported, but now the fate of the order is unclear. The country's health secretary told local media in December last year that it expected the first batch of the jab by February.

India plans to vaccinate some 300 million people on a priority list by August.

It has recorded the second-highest number of infections in the world, with more than 10.3 million confirmed cases to date. Nearly 150,000 people have died.

Both vaccines approved on Sunday can be transported and stored at normal refrigeration temperatures.