The reports said Yuval Diskin, the head of Israel's Shin Bet internal security service, told Olmert's cabinet that militants planned to attack the Israeli leader's convoy as it sped to a meeting with Abbas in the West Bank town of Jericho in August.
A senior Palestinian security official told Reuters Palestinian authorities detained and questioned three men for two months at the request of the Shin Bet.
The men were released last week, sparking an Israeli protest. In response, Palestinian authorities detained the three men for further questioning, the security official said.
Olmert's spokeswoman, Miri Eisin, refused to comment on the reports.
The YNet Web site quoted an official in Olmert's office as saying: ''We view very gravely the fact that the Palestinian Authority released the cell members who were in its custody. We have protested strongly.'' The meeting between Olmert and Abbas on August 6 went ahead as planned under heavy security at a resort hotel in Jericho in the occupied West Bank.
All of the other meetings between the leaders have been held in Jerusalem.
REUTERS SKB AS1533