April 26 (Reuters) - U.S. drugmaker Merck & Co joined Gilead Sciences on Tuesday in lending support to India as the world's second-most populous country scrambles to address drug shortages and bring a raging new wave of COVID-19 cases under control.

Gilead said it would give India at least 450,000 vials of its antiviral drug remdesivir, while Merck said it was partnering with five Indian generic drugmakers to expand production and access to its experimental COVID-19 drug molnupiravir.

With the death toll from COVID-19 racing towards the 200,000-mark in India, medical supplies from across the world are being flown into the country to help overburdened hospitals struggling with a severe shortage of life-saving oxygen and drugs.

Nations including Britain, Germany and the United States have pledged support, while the World Health Organization said it was working to deliver 4,000 oxygen concentrators, calling the situation in India "beyond heartbreaking".

In addition, India expects to secure the biggest chunk of the 60 million AstraZeneca COVID-19 vaccine doses that the United States will share globally, two Indian government sources told Reuters.

Gilead said on Monday it would help boost the production of remdesivir in India, where the drug is approved for restricted emergency use to treat severe COVID-19 cases, by offering technical assistance to its manufacturing partners.

Seven Indian companies have licensed the drug from Gilead, with a total installed capacity of about 3.9 million units per month. Gilead said the companies were scaling up their batch sizes and adding new manufacturing facilities and local contract manufacturers.

Hospitals are facing supply shortages of remdesivir due to indiscriminate use. The drug is being sold at over 10 times its listed price in the black market, stoking fears of hoarding as people queue up outside clinics and millions take to social media to secure supplies.

Earlier this month, India banned the export of the drug and the active pharmaceutical ingredients (API) used to make it.

The WHO in November issued a conditional recommendation against the use of remdesivir in hospitalised patients due to doubts about its effectiveness in treating COVID-19, but India has continued to use it.

A senior Indian government health official said last week that remdesivir is only for those patients who need oxygen. "I am appealing that the hype over this medicine should be decreased, and it should be used in a rational manner," Vinod Kumar Paul said.

Merck said on Tuesday its partnership with Indian drugmakers, including Cipla Ltd and Sun Pharmaceutical Industries Ltd, will give the companies license to supply molnupiravir to India and more than 100 low- and middle-income countries after the treatment is authorized.

Merck also said it would donate more than $5 million worth of oxygen-production equipment, masks, hand sanitizers and financial aid to India.

(Reporting by Trisha Roy in Bengaluru and Sayantani Ghosh in Singapore; Additional reporting by Anuron Mitra, Manojna Madipattla and Ankur Banerjee; Editing by Arun Koyyur and Saumyadeb Chakrabarty)