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A jet linked to sanctioned Russian oligarch Roman Abramovich arrived in Istanbul from Israel on Monday, shortly after he was seen in Tel Aviv's Ben Gurion International airport.
Mr Abramovich was among seven Russian billionaires added to a British sanctions list last week to try to isolate President Vladimir Putin over Russia's invasion of Ukraine. EU diplomats have embraced a similar move.
The Russian oligarch, who also holds Israeli and Portuguese citizenship, has denied having close ties to Mr Putin.
A photograph obtained by Reuters showed Mr Abramovich, the owner of Britain's Chelsea soccer club, sitting in Tel Aviv airport's VIP lounge with a face mask pulled down over his chin.
Reuters could not verify whether he boarded the flight.
A source said the plane used by Mr Abramovich flew into Ben Gurion late on Sunday from Moscow.
Flight-tracking website Flightradar24 said the aircraft, which has the tail number LX-RAY and is a large Gulfstream business jet, landed in Istanbul on Monday after leaving Israel.
It was not scheduled to fly on from Istanbul after landing and remained there, flight plans show. The plane had also been in Turkey last week, according to tracking data.
Istanbul, Turkey's largest city, is home to the head office of AB Grup Holding, a company run by Muhsin Bayrak, who has publicly expressed interest in buying Premier League club Chelsea from Mr Abramovich.
Mr Bayrak has interests in building, energy and real estate, and has said he was talking to Mr Abramovich about the sale process.
Mr Abramovich said last week he was selling the London club, but that sale is now on hold with Chelsea operating under a special government licence, and the Premier League board has disqualified him as a club director.
Chelsea's Roman Abramovich and other Russians have assets frozen after UK sanctions
A British Transport ministry source said on Friday that Britain was searching for helicopters and jets belonging to the sanctioned oligarchs.
Property including opulent yachts worth hundreds of millions of dollars have been seized by authorities in Europe in recent days.
Tracking sites Marine Traffic and Vessel Finder say Mr Abramovich's $600 million yacht Solaris had been off Montenegro heading to Istanbul.
But later the vessel's status changed to "awaiting orders" and its destination was removed
Nato member Turkey has close ties with Kyiv and Moscow and has balanced its criticism of the invasion of Ukraine with its opposition to western sanctions on Moscow.
Russia calls its movement of troops into Ukraine a "special military operation".
Victoria Nuland, the US undersecretary of state for political affairs, told Israel's Channel 12 on Friday that Washington was asking Israel to join in financial and export sanctions against Russia.
Putin vows to overcome western sanctions
Speaking in Slovakia, which borders Ukraine, visiting Israeli Foreign Minister Yair Lapid said Israel "will not be a route to bypass sanctions imposed on Russia by the United States and other western countries".
Mr Lapid did not say directly whether Israel was considering its own sanctions.
But he said the Foreign Ministry was "co-ordinating the issue together with partners including the Bank of Israel, the Finance Ministry, the Economy Ministry, the Airports Authority, the Energy Ministry and others".
Asked for further details, the Bank of Israel said that it was "constantly monitoring developments in the payments systems, the markets, and the financial system".
Any Israeli sanctions could complicate efforts by Israeli Prime Minister Naftali Bennett to mediate the Russian-Ukrainian crisis.
Mr Bennett held talks in Moscow with Mr Putin on March 5 and has spoken several times by phone with Ukrainian President Volodymyr Zelenskyy.
A senior Israeli official said Mr Abramovich was not involved in the mediation.
Sympathy for Ukraine is strong in Israel.
The country's Yad Vashem Holocaust memorial in Jerusalem said on Thursday that it had suspended a strategic partnership with Mr Abramovich after Britain's move against him.
