Allen & Overy (A&O) and Vinson & Elkins (V&E) have taken roles on the $5.5bn (£3.3bn) STAR refinery venture, the largest ever project financing in Turkey.

STAR is a joint venture between Azerbaijan's State Oil Company and the country's Ministry of Economy and Industry, to develop and finance a greenfield oil refinery in Turkey on the Aegean Sea.

The project, the first Turkish refinery to be developed since 1972, is expected to start operation in 2018 and will manufacture petroleum products such as diesel oil, jet fuel and liquefied petroleum gas.

As well as being the largest project financing in Turkey's history, the deal is notable for the range and diversity of lenders, which included export credit agencies from Italy, South Korea, Japan, the US and Spain, and 16 commercial banks from Europe and Asia.

A&O is advising the syndicate of lenders, with Istanbul partner Charles Lindsay and London partner Lorraine Bayliss leading a team which included six associates.

Lindsay said the deal was "a real vote of confidence in the local market", adding: "This is the most significant deal we have worked on since opening our office in Istanbul in 2012.

"It marks a real watershed both in terms of our own progress in the Turkish legal market and of Turkey's progress in the global infrastructure market."

Although A&O has a local association with Istanbul firm Gedik & Eraksoy, Turkish counsel to the lenders is provided by Paksoy.

Meanwhile, the London office of V&E is providing international counsel for STAR, with global project finance practice co-head Nabil Khodadad heading a team that includes partner Andrew Nealon, and which last year acted on the $4bn Surgil gas and petrochemicals project in Uzbekistan.

The Azerbaijani venture was advised on Turkish law matters by local counsel YukselKarkinKucuk.

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