ISTANBUL (AFP) - Turkey on Monday said it had summoned the US charge d'affaires in Ankara to demand an explanation over a German report that Washington has spied intensively on Turkish leaders since 2006.

The Der Spiegel German weekly reported that as well as sharing intelligence with Nato partner Turkey, the United States and its ally Britain have been conducting extensive electronic surveillance on the Turkish leadership.

The report said that the information was based on documents released by the fugitive former National Security Agency (NSA) operative Edward Snowden who has taken asylum in Russia.

"The US charge d'affaires has been summoned to the foreign ministry to demand an explanation," Deputy Prime Minister Bulent Arinc told reporters in Ankara in televised comments.

The new US ambassador to Turkey, Mr John Bass, is yet to arrive in Ankara.

Der Spiegel said starting in 2006, the NSA began a major surveillance operation aimed at hacking into the computers of Turkey's leadership.

The aim was to glean information about the strategic intentions of the Turkish leadership under Mr Recep Tayyip Erdogan, who on Thursday was inaugurated as president after over a decade as prime minister.

It said that the US also spied on Turkey's embassy in Washington and its mission at the United Nations in New York.

According to Der Spiegel, the NSA placed "Turkey at the level of Venezuela, and even ahead of Cuba, in terms of US interest in intelligence collection."

The information was shared with the key intelligence partners of the US - Britain, Canada, Australia and New Zealand.

Der Spiegel said Britain had already developed its own operations in Turkey, with its GCHQ surveillance agency eavesdropping on political targets in the country.

Turkey has already expressed anger over a previous report in Der Spiegel that Germany had been spying on its Nato ally for years.

Der Spiegel also said that at the same time there had been very tight cooperation between the US and Turkey on intelligence, particularly on Kurdish militants fighting an insurgency in Turkey's southeast.

It said that one NSA document bluntly described Turkey as both a "partner and a target".