Japanese electronics products manufacturer Toshiba Corp said it will invest 700 billion yen ($8.57 billion) in environment and energy sectors over the next three years to meet demand from infrastructure projects, business daily Nikkei said.

The strategy, including mergers and acquisitions, will expand the company's 2011-2013 capital and research-and-development budget to more than 3 trillion yen, up 50 percent from 2008-10, the paper reported.

The company has stepped up efforts to tap the markets for solar and other renewable sources of energy, as well as smart grids, Nikkei said.

Toshiba recently purchased unlisted Swiss smart-meter manufacturer Landis+Gyr for around 190 billion yen.

Keeping in tune with this, Toshiba said it plans to become the top shareholder in South Korean firm Unison Co, wherein, the Japanese firm will buy some 3 billion yen in Unison convertible bonds as the first step, the daily reported.

It will later raise its stake in the producer of wind power generation equipment to about 30 percent in about a year, said Nikkei.

Toshiba also plans to boost output at a lithium ion battery plant in Kashiwazaki, Niigata Prefecture, in anticipation of higher demand for use in smart-grid systems, the paper said.

Recently, Toshiba's nuclear-focused strategy has suffered a serious setback since the accident at the Fukushima Daiichi power plant, the Nikkei reported.

(Reporting by Arpita Mukherjee in Bangalore; Editing by Joyjeet Das)