Mitsui offered to pay S$1.40 per share for Portek, higher than a bid announced last month by the Philippines' International Container Terminal Services Inc , which offered to pay S$1.20.
Portek operates and manages ports in Indonesia, Algeria, Malta, Gabon and Rwanda. Mitsui said in a statement the deal would help it improve productivity and efficiency in its logistical operations around the world.
The deal is yet another instance of Japanese companies expanding overseas after the March earthquake and tapping into rapidly growing Asian and African markets.
There was no immediate comment from Portek, but the Singapore exchange suspended its shares on a company request after the stock surged over 6.0 percent from the previous close.
Mitsui said Portek's majority owners, who control 51.3 percent of the firm, had made an irrevocable agreement to accept the offer.
A source close to the deal told Reuters it was unlikely that ICTSI would launch a counter offer to Mitsui's bid due to the irrevocable undertaking.
BATTLE FOR CONTROL STILL ON?
But Kim Eng Securities noted that ICTSI already controlled about 17 percent of Portek and the battle for control need not have ended.
"This is likely to be a friendlier bid than ICTSI, since Portek's management had been engaged prior to the bid," Kim Eng said in a note.
It added: "We do see synergies between ICTSI and Portek's business and believe the former would still be interested in a price higher than Mitsui's.
"However, minority shareholders may want to cash out immediately, since any further battle for control could turn into a deadlock with Mitsui already effectively controlling more than 50 percent of the shares."
Portek shares went as high as S$1.405 on Wednesday before the trading halt.
Nomura is advising Mitsui on the deal while HSBC is advising ICTSI.
Portek has hired Malaysian bank CIMB to advise it on the potential takeover.
Prior to Mitsui's bid, Portek's shares had surged by around 86 percent since ICTSI made its offer in early June.
Mitsui said it intends to delist Portek from the Singapore Exchange. (Reuters)
