* Govt to buy 11 mln doses for $2.72/shot - source

* Federal govt to bear cost of vaccinating first 30 mln people -PM

* India has world's second highest coronavirus caseload

MUMBAI/BENGALURU, Jan 11 (Reuters) - India has signed a purchase order with vaccine producer Serum Institute to supply some 11 million doses of AstraZeneca's COVID-19 vaccine, a source said on Monday, the first step in one of the world's largest such programs.

Prime Minister Narendra Modi's government would buy the shots at 200 rupees ($2.72) per dose, said the source, who had been briefed on the matter.

Serum, the local maker of the Oxford University/AstraZeneca shot, would start sending the doses to government storage facilities on Tuesday, the source added.

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

The government has also signed a purchase deal with Indian firm Bharat Biotech for its COVID-19 vaccine, TV channel CNBC reported, citing unnamed sources. Approval of that home-grown shot has been criticized for lack of efficacy data.

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

India aims to secure 600 million doses for a vaccination drive aiming to inoculate 300 million people considered at highest risk over the next six to eight months.

The program is expected to begin on Jan. 16.

Modi said the federal government would pay for vaccinating 30 million people in the first phase, while four more shots could be developed in coming months.

In closing remarks after meeting India's state heads, Modi said priority in the second phase would be given to people over 50 and those suffering from other diseases that put them at risk.

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

India's drug regulator gave emergency use approval for the AstraZeneca and Bharat Biotech vaccines earlier this month.

Two others - Zydus Cadila's ZyCoV-D and Russia's Sputnik V - are still in trials in India.

($1 = 73.4130 Indian rupees) (Reporting by Euan Rocha in Mumbai and Sachin Ravikumar in Bengaluru; Editing by Arun Koyyur and Andrew Cawthorne)