Chinatrust, in final talks to buy AIG's Taiwan unit Nan Shan, has attracted more foreign interest than expected to subscribe to its T$44.3 billion ($1.4 billion), private placement, an executive said.

At least five foreign investors have expressed interest in subscribing to the entire $1.4 billion Chinatrust rights issue, Chief Investment Officer Daniel Wu told Reuters on Monday.

Each of the investors has expressed interest in buying the entire rights issue, which would account for a 20 percent stake of Chinatrust, Wu said via telephone.

The fund to be raised would be used to strengthen our financial structure, including acquiring Nan Shan, he said, adding Chinatrust, Taiwan's top credit issuer, aimed to complete the rights issue before end of this year.

In early September, Chinatrust said it planned to raise more cash on top of the $1.4 billion private placement by way of global depository receipts or subordinated debt.

Chinatrust is competing with Primus Financial to acquire Nan Shan. Both firms are in talks with American International Group.

No timetable has been set on when AIG will pick the winner.

Chinatrust had offered $2.4 billion for Nan Shan, AIG's most expensive asset for sale in Asia so far, a source said in early September.

Wu's comments came after the Taiwan market closed on Monday. Shares of Chinatrust ended 0.68 percent lower, underperforming the main TAIEX index's 0.37 percent rise.

(Reporting by Faith Hung; Editing by Andrew Macdonald)