Israeli Prime Minister Benjamin Netanyahu secretly flew to Saudi Arabia on Sunday to meet Crown Prince Mohammed bin Salman, Israeli media report.
Flight-tracking data showed a business jet previously used by Mr Netanyahu travelled to the Red Sea city of Neom.
There was no official confirmation, but an Israeli minister said he had been told about it by the foreign ministry.
It would be the first known meeting between leaders of the historical foes, whom the US wants to normalise ties.
President Donald Trump has recently brokered deals establishing diplomatic relations between Israel and the United Arab Emirates, Bahrain and Sudan.
Saudi Arabia cautiously welcomed those moves, but indicated it would wait until there was a peace agreement between Israel and the Palestinians.
Also on Monday, a delegation of senior Israeli officials travelled to Sudan on what would also be the first such visit to a formerly hostile country, an unnamed Israeli official confirmed.
The sides are expected to map out areas of co-operation, after Mr Trump announced last month that Sudan had agreed to normalise ties with Israel.
Citing unnamed Israeli sources, Israeli public broadcaster Kan and other media reported that Mr Netanyahu and the head of the Mossad intelligence service, Yossi Cohen, attended talks in Saudi Arabia on Sunday evening with Crown Prince Mohammed and US Secretary of State Mike Pompeo.
A senior Saudi adviser told the Wall Street Journal that the leaders discussed several issues, including normalisation of ties and Iran, but that no substantial agreements were reached.