Billionaire Li Ka-shing, pictured in 2015.

Li Ka-shing's Cheung Kong Infrastructure (CKI) has sweetened an $11.6 billion offer to buy the 61 percent of Power Assets it doesn't already own in a rare concession by the Asian tycoon to independent investors unconvinced by his original plan.

CKI, the infrastructure arm of Li's empire, said in a statement late on Wednesday that after feedback from a number of shareholders, it would raise the share-swap ratio in the offer by 2.5 percent, hoisting the deal's value to $12.4 billion. It is also raising a planned special cash dividend by 50 percent.