(Corrects to add missing letter in first paragraph)

* Macquarie's $2.6 bln offer conditional on due diligence

* Approach could spark bidding war for Vocus, share rise

* Share price reflects risk of bid withdrawal after due diligence

SYDNEY, Feb 8 (Reuters) - Australia's Vocus Group on Monday said Macquarie's funds had lodged a non-binding offer to acquire the fibre network owner for A$3.42 billion ($2.62 billion) and would open its book to the firm, sending its shares almost a fifth higher.

The approach from Macquarie Infrastructure and Real Assets Holdings (MIRA) - one of at least three since 2019 - carries a price of A$5.50 per share, already the highest from any recent suitor, and could spark a competitive process for the telecom company.

Vocus' shares rose to their highest since November 2016 but at midday were trading at A$4.98, below MIRA's offer, which represents a 25.6% premium to its last close, as investors priced the risk that the suitor walks away after seeing the books, as it has happened with recent approaches.

"The Board has concluded that it is in the best interests of Vocus shareholders to explore the potential for a transaction with MIRA," the company said in a statement to the exchange.

The offer comes a year and half after power supplier AGL Energy and Swedish private equity firm EQT Infrastructure dropped similar proposals to take over the company following brief due diligence periods.

"We believe a situation like that happening again would be perceived very negatively, with investors likely questioning what within the company is driving interest away," JPMorgan analyst said.

"While on the one hand, the actions by MIRA may elicit competing bids given the interest shown in Vocus in the past, there is clearly no guarantee that the process will lead to a full transaction."

In 2017, takeover negotiations with private equity firms KKR and Affinity Equity Partners, which had made separate bids for the company, also ended after a period of due diligence did not result in an acceptable deal.

MIRA, part of Macquarie Group's asset management arm, already holds interests in the telecom sector with a stake in mobile tower owner Axicom, formerly Crown Castle Australia.

MIRA did not return a request for comment.

($1 = 1.3053 Australian dollars) (Reporting by Paulina Duran in Sydney and Arpit Nayak in Bengaluru; Editing by Diane Craft, Sam Holmes and Michael Perry)