MUMBAI/BENGALURU: India has signed a purchase order with vaccine producer Serum Institute to procure AstraZeneca's COVID-19 vaccine, a source said on Monday, the first step in one of the world's largest vaccination programmes against the novel coronavirus.

Local television channel CNBC-TV 18 said the order was for 11 million doses and the government would buy the shots at 200 rupees ($2.72) per dose.

The government has also signed a purchase agreement with Indian firm Bharat Biotech for its COVID-19 vaccine, the news channel reported, citing unnamed sources.

Representatives for Serum, Bharat Biotech and India's health ministry did not immediately respond to Reuters requests for comment.

India aims to secure 600 million doses for its vaccination drive that aims to inoculate 300 million citizens over the next six to eight months. The programme is expected to begin on Jan. 16.

Serum, the world's largest producer of vaccines, has stockpiled 50 million doses for immediate distribution.

India's drug regulator had given emergency use approval for both vaccines earlier this month. Two other vaccines - Zydus Cadila's ZyCoV-D and Russia's Sputnik V - are still in trials in India.

Meanwhile, the government's decision to approve the homegrown Bharat Biotech vaccine has met with criticism from health experts for the lack of data showing its efficacy.

At nearly 10.5 million, India has the world's second highest number of novel coronavirus infections behind the United States, although its rate of increase in cases has been slowing.