Tenaga Nasional Bhd , Malaysia's biggest power group, said on Friday it was offering 644.22 million ringgit ($181 million) to buy the remaining shares in port operator Integrax Bhd that it does not already own.

The offer, at 2.75 ringgit a share, represents a 19 percent premium over Integrax's closing price of 2.31 ringgit on Friday.

Tenaga - which counts Malaysia's state investor Khazanah as its biggest investor - is currently the largest Integrax shareholder, with a 22.12 percent stake.

It plans to delist Integrax from the Kuala Lumpur stock exchange if it takes control, it said in a stock exchange filing.

Integrax owns the Lumut Port, on the west coast of Peninsular Malaysia in the state of Perak, according to its website.

Tenaga shares, which have risen about 20 percent over the past year, closed down 0.28 percent lower at 14.16 ringgit on Friday.