(Reuters) -Australia’s AusNet Services said on Monday it had opened its books to an affiliate of Canadian infrastructure investor Brookfield Asset Management after it received a higher non-binding buyout proposal of A$9.57 billion ($6.95 billion). The deal comes amid a spike in mergers and acquisitions activity over the past year in Australia, with record-low interest rates encouraging institutional investors and companies to chase higher valuations. AusNet, which owns and operates Victorian electricity transmission network, revealed that the revised A$9.57 billion bid came after it had rejected two unannounced previous bids last month from the Brookfield affiliate that valued it at up to A$9.38 billion.The revised here A$2.50 per share offer - a 26.3% premium to AusNet"s last close - was up from proposals of A$2.35 and A$2.45 tabled earlier. That sent shares of the Australian energy infrastructure firm soaring, advancing as much as 20.7% to A$2.39 and marking their best intraday percentage gain. AusNet said it had agreed to grant Brookfield access to its books and conduct due diligence on an exclusive basis.“Should Brookfield make a binding offer at A$2.50 per share then ... it is AusNet board’s current intention to unanimously recommend that shareholders vote in favour of the proposal in the absence of a superior proposal,” AusNet said in a statement. AusNet, owned by Singapore’s Temasek Holdings and China’s State Grid Corporation, said the deal is subject to foreign investment review board’s approval. ($1 = 1.3765 Australian dollars)