Vallibel Erathne said in a stock exchange filing that it was selling five million shares in Didul.
Managing director Leel Wickremerachchi declined to reveal the name of the buyer saying it was an unlisted company. But he said it was not a 'group' company.
The shares were carried in the books of Vallibel at 10 rupees indicating a capital gain of 135 million rupees.
The board is yet to decide on the capital gain made from the sale, Wickremarachchi said.