Qatar has bought a stake in Credit Suisse as part of its strategy to invest $15 billion (£7.5 billion) in European and American banks.

Sheikh Hamad bin Jasim bin Jaber al-Thani, the Gulf state's Prime Minister and chief executive of the Qatar Investment Authority (QIA), said: “We have a relation with Credit Suisse and we bought some of the stock from the market.”

Sheikh Hamad did not reveal the size of the stake, because the deal was still in process. Under Swiss stock exchange rules, companies must reveal the identity of any shareholder with a stake of more than 3 per cent. Credit Suisse shares closed up SwFr1.75, or 3.2 per cent, at SwFr56.75.

At the World Economic Forum in Davos, Switzerland, last month, Qatar said that it wanted to invest up to $15 billion in financial stocks hit by sub-prime writedowns.

Credit Suisse has a long relationship with Qatar. It was the first European bank to acquire a licence for the Qatar Financial Centre, a self-regulated business park designed to attract lenders to the country, which is eager to diversify its economy away from oil and gas.

Last year QIA, which is estimated to manage about $60 billion, tried to buy J Sainsbury, the supermarket chain. Deteriorating credit markets and the demands of the company's pension fund forced it to abandon the attempt in November.

State-managed funds from countries such as Qatar and Abu Dhabi are worth an estimated $3.2trillion, their value buoyed by record oil prices and rising currency reserves. Morgan Stanley estimates that these funds may be worth $12trillion by 2015.

Sovereign wealth funds from the Middle East and Asia have invested their large cash reserves heavily in Western banks hit by the global credit crunch and sub-prime writedowns. Already, they have taken stakes in banks such as Citigroup, Morgan Stanley and UBS.

The Kuwait Investment Authority, which manages an estimated $250 billion, said last month that it was keen to invest in European banks.

The QIA refused to expand on the comments made by Sheikh Hamad.

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