OSAKA (Kyodo) -- Panasonic Corp. plans to sell three semiconductor assembly plants in Southeast Asia to Singaporean chip manufacturer United Test and Assembly Center Ltd., sources close to the matter said Friday.

The move is part of efforts by the Japanese electronics manufacturer to accelerate outsourcing of its slumping semiconductor manufacturing operation. Last month, the company said it will sell off three of its semiconductor plants in central Japan to an Israeli chipmaker.

Panasonic aims to unload the plants in Indonesia, Malaysia and Singapore by the end of fiscal 2014 starting April, with workers at the plants to have their employment transferred to UTAC, the sources said. Other than the three plants, the company is also considering the sale of a plant in China, they said.

The three plants subject to the sale assemble semiconductors for electronics products including flat-panel televisions and digital cameras, but their operating rates have been low due to sluggish sales of digital home electronics products.

After selling the three plants, Panasonic will purchase finished products from UTAC, which assembles and tests semiconductors, the sources said.

Regarding its domestic semiconductor plants, Panasonic will spin off three plants -- two in Toyama Prefecture and another in Niigata Prefecture -- into a separate entity, in which Tower Semiconductor Ltd. has agreed to purchase a 51 percent stake.

The company also plans to close another plant in Okayama Prefecture which makes components related to semiconductor lasers by the end of March to trim losses in the semiconductor business.