Five Australian banks are among 18 defendants named in a lawsuit brought by a pair of US hedge funds that centres on allegations of manipulating short term interest rate benchmarks.Australia's four major banks and Macquarie have been sued in the US District Court by two US hedge funds and a derivatives trader.The applicants are Sonterra Capital Master Fund, Frontpoint Financial Services and some of its related funds and also Florida-based derivatives trader Richard Dennis.The two hedge funds are also applicants in a corresponding class action, begun in early July, amid allegations of a "massive conspiracy" to rig the prices of financial derivatives linked to Singapore's benchmark interest rates.In the case of the Australian banks, the US hedge funds' claim relies heavily on material uncovered, and beginning to reach the public domain, in civil cases bought by the Australian Securities & Investments Commission against ANZ, NAB and Westpac.In the statement of claim for the class action the plaintiffs assert that "collusive communications released in ASIC's filings show that defendants fixed BBSW-based derivatives prices using multiple means."These included "engaging in manipulative money market transactions during the BBSW fixing window; making false BBSW rate submissions that did not reflect actual transaction prices; uneconomically buying or selling money market instruments at a loss to cause artificial derivatives prices; and sharing proprietary information to align interests and avoid conduct that could harm conspiracy members." ANZ said in a statement it would be "vigorously defending the US class action complaint". AISC, ANZ, NAB and Westpac are all due on court next week for a further preliminary hearing on the ASIC matter.