The deals came as the owner of the world's biggest refining complex aims to make India a hub for low-cost solar manufacture. In June, it committed to invest $10.1 billion in clean energy over three years.
Through its unit Reliance New Energy Solar Ltd, Reliance Industries is buying Norwegian-headquartered solar panel maker REC Solar Holdings for $771 million from China National Bluestar and an up to 40% stake in India's Sterling and Wilson Solar.
REC has patented technology and opens up the export market for Reliance's solar business, analysts at Jefferies said in a note on Sunday.
"REC's long operating history in Europe and the U.S. opens up the possibility of RIL exporting to these geographies," Jefferies said.
Shares of Sterling and Wilson Solar jumped 17% to their highest in nearly two years in heavy-volume trade, as the Reliance deal adds to its growing portfolio of projects globally.
About 11.9 million Sterling and Wilson shares had changed hands by 0508 GMT, 3.4 times their 30-day average.
Sterling and Wilson Solar has about 11.4 GWp of solar power projects across the world, and provides operations and maintenance services, according to a statement.
Reliance shares have risen about 35% this year, as of last close, while Sterling and Wilson stocks have gained 67.4%.
(Reporting by Vishwadha Chander in Bengaluru; Editing by Subhranshu Sahu)