Hungarian police say a detained Palestinian has told them he planned to bomb the Holocaust Museum in Budapest.
Israeli President Katsav (left) with Hungarian counterpart Ferenc Madl
Police denied any link with the current visit to Hungary by the Israeli President, Moshe Katsav.
Mr Katsav arrived in Hungary on Tuesday for a three-day visit, during which he is scheduled to inaugurate the new Holocaust Museum.
Two Syrians were also detained for
questioning as police carried out house searches in Budapest.
"There is no connection whatsoever between the Israeli president's visit and the particular police action taken today," said police chief Laszlo Salgo.
Earlier, a senior official in Mr Katsav's office, Moshe Mizrahi, told the Associated Press that the three were arrested "on suspicion that they were trying to kill the president".
However, he said Mr Katsav's visit would continue as planned.
Israeli embassy officials in Budapest denied reports that Mr Katsav's schedule for the visit had been changed several times because of security concerns.
The Iranian-born Mr Katsav was elected president in 2000.
He has served in two right-wing governments, but is regarded as a moderate compared to his Likud-party colleague, Prime Minister Ariel Sharon.
Israeli presidents have a largely ceremonial role.