They were planning to bomb several embassies and kill some diplomats. From AP, :
At a news conference, Interior Minister Elias Murr identified the leaders of the plot as Ahmed Salim Mikati and Ismail Mohammed al-Khatib, both Lebanese, and said they had eight Lebanese and Palestinian accomplices, who were also arrested on Friday night.
Khatib “is an al-Qaida operative … his role was to recruit fundamentalist youth to carry out operations against coalition forces in Iraq,” Murr said. He added that one of al-Khatib’s recruits was a Lebanese citizen who was killed in Iraq on Sept. 17.
Prosecutor-General Adnan Addoum told the press conference that both al-Khatib and Mikati had “links to al-Qaida,” the militant group led by Osama bin Laden.
The two leaders and their accomplices “cooperated and exchanged information” in planning simultaneous bombings of the Italian and Ukrainian embassies and several Lebanese security and judicial targets, Addoum said.
An Interior Ministry statement said the suspects planned to pack a car with 660 pounds of TNT and use it to blow up the Italian Embassy in Beirut.