NEW DELHI (Reuters) - India successfully launched 20 satellites in a single mission on Wednesday, with most of them set to serve international customers as the South Asian country pursues a bigger share of the $300 billion global space industry.

It was the most satellites India has put in space at one go, though Russia set the record of 37 for a single launch in 2014.

Prime Minister Narendra Modi described the launch as "a monumental accomplishment" for the state-run Indian Space Research Organisation (ISRO).

Modi is bullish about India's space research program and has repeatedly praised the efforts of scientists who two years ago pulled off a low-cost mission to send a probe to orbit Mars that succeeded at the first attempt.

The launch of PSLV-C34, carrying 20 satellites in a single payload including the Cartosat-2 series satellite and 19 co-passenger satellites, was like "allowing birds to fly in space", ISRO chairman Kiran Kumar said.

Polar Satellite Launch Vehicle or PSLV is India's workhorse launch vehicle, and has so far successfully carried 113 satellites, of which 74 were for international customers, ISRO said on its website.

Of the satellites launched on Wednesday, all except three are for international customers, with the United States accounting for more than half.

(Reporting by Malini Menon; Editing by Douglas Busvine and Simon Cameron-Moore)