A Thai group said Tuesday it was exploring a bid for Singapore's Fraser and Neave (F&N) conglomerate, complicating Dutch beer giant Heineken's takeover of a major Asian brewer partly owned by F&N.

Thai Beverage, the Singapore-listed maker of Chang Beer, said in a statement that "a party acting in concert with the company is exploring the possibility of making an offer for F&N". It did not identify the partner.

Heineken is offering Sg$5.6 billion (US$4.53 billion) for F&N's 40 percent stake in Asia Pacific Breweries (APB), which makes the popular Tiger Beer and other alcoholic beverages.

Heineken already owns 42 percent of APB.

F&N's board has recommended acceptance of the Heineken offer and asked shareholders to approve it in a September 28 meeting.

But Thai Beverage has been steadily building up its holding in F&N and its stake now stands at 29 percent, just one percentage point below the threshold that will trigger a mandatory offer for all outstanding shares it does not own.

"It seems ThaiBev is serious about acquiring F&N and is looking to bring onboard partners to help it acquire the soft drinks manufacturer," said Justin Harper, market strategist with IG Markets in Singapore.

"But shareholders may still prefer selling F&N's APB stake to Heineken rather than trust a half-cocked effort by the Thais to acquire the company at the eleventh hour with another interested party," he said.

Heineken was forced to raise its bid to Sg$5.6 billion from Sg$5.1 billion to fend off a rival party headed by Thai billionaire Charoen Sirivadhanabhakdi, who controls Thai Beverage.