Italian police arrested seven Lebanese students last weekend whom they strongly suspect of planning to blow up the United States Embassy in Rome in a truck-bomb suicide attack.
The students are believed to be members of the Islamic Jihad movement which claimed responsibility for the bombing in Beirut last year of the American Embassy, US Marine guards command, and the French contingent of the multinational peacekeeping force.
Rome police chief Marcello Monarca said Wednesday there was ''irrefutable proof'' that the seven had planned to attack the US Embassy.
Italian police had been working on the basis of the Nov. 18 arrest in the Zurich airport of Hani Hussain Atat, a Lebanese. Mr. Atat, who held a ticket to Rome, was found to be carrying four and a half pounds of explosive similar to that used in the Beirut bomb attacks.
The seven students, who were enrolled in Rome University, lived in two apartments in the coastal town of Ladispoli, some 25 miles north of Rome. In a surprise search there Saturday night, police found pro-Khomeini propaganda pamphlets and Islamic Jihad literature.
They also found a map of the US Embassy, situated on the fashionable Via Veneto in downtown Rome. Arrows marked details such as the positions of guards, television cameras, and protective pillars and concrete blocks - recent additions to protect against possible truck bomb attacks. The map showed the entrance to the underground garage below the Marine guards residence which, according to one theory, is where the bomb-laden truck would have caused the most damage.
Although the arrests were made Saturday, the news was only released on Tuesday, in order to give Rome's antiterrorist police time to work on any contacts the group may have had with Italian or foreign armed movements, and to search for further explosives.
While there are no reports of the explosive material or the truck the group planned to use, there are reports that they were known to move in ''foreign circles'' in the university for foreigners in Perugia, a central Italian town where past police searches have turned up groups of foreign terrorists.
The seven are being held in isolation in a police barracks instead of jail. They are charged with constituting an armed group and planning a massacre. Their case is being handled by one of Italy's top antiterrorist magistrates, Domenico Sica. Thus far, they have refused to answer any questions which he has put to them.
''We are certainly taking this attempt very seriously,'' said a US Embassy spokesman, ''and I must say that the Italians get all the credit for their follow-up work on the first arrest in Switzerland.''
The US ambassaador to Italy, Maxwell Rabb, expressed his gratitude to the Italian police, adding that ''once again the Italians have set an example for the world in how to defeat the threat of terrorism.''