China's Bohai Leasing Co Ltd has offered to buy Irish rival Avolon for $2.55 billion, a 55 percent premium over its December initial public offering, the Irish firm said.

Avolon said it was considering Bohai's $31 per share offer and a rival $30 per share bid from an unidentified bidder and was in contact with both parties.

Bohai, a unit of aviation and shipping conglomerate HNA Group, earlier in July offered to buy 20 percent of Avolon for $429 million at $26 per share, an offer that is now being put to shareholders.

But it offered to buy the whole company when it was informed of the third party bid.

"Avolon's Board of Directors has not accepted or rejected either offer and continues to carefully evaluate these ... and has authorized its financial advisors to continue negotiations with both," Avolon said in a statement.

The purchase would boost HNA's access to a global aircraft leasing market dominated by GE Capital and AerCap Holdings NV.

Chinese lessors, mostly backed by state-owned banks, have been expanding in recent years as large carriers such as Hainan Airlines Co Ltd, Air China Ltd, China Eastern Airlines Corp Ltd and China Southern Airlines Co Ltd opened more routes at home and overseas.

Ahead of Avolon's IPO, China Investment Corp (CIC) and AVIC Capital Co Ltd were in talks to acquire Avolon.

Avolon, which was founded by leasing entrepreneurs Domhnal Slattery and John Higgins in 2010, owns or managed 152 aircraft at the end of June and had over 100 more on order.