Greek police evacuated a train travelling between Athens and the Greek-Bulgarian border and three ferries on Thursday following bomb alerts, police said.
Nearly 40 passengers travelling between Greece's second city Salonika and the northeastern city of Alexandroupolis were ordered off the train at the station in the town of Drama.
Anti-terrorist experts rushed to the scene to search the train. The bomb alert was given in an anonymous call to a train station near Drama.
"The train left Drama station three hours after the alert," station master Kleanthis Karayannidis told reporters.
Two ferries, the Theofilos and the Possidon Hellas, set to leave Greece's main port Piraeus for the islands of Lesbos and Egina respectively were also evacuated after bomb alerts, police said.
No explosive devices were found during a search, according to Yannis Xidis of the merchant marine ministry's press department.
A third ferry bound for Piraeus was also searched after a bomb alert but no explosives were found and the Lato left the Crete island port of Souda almost an hour late.
The four alerts came as Olympic organizers, facing a race against the clock to get ready for the Athens Games, heaved a sigh of relief when the Olympic torch ceremony went off on cue.
Security was tight around the ruins of Ancient Olympia, where the Games were born in 776 BC, when Olympic high priestess Thalia Prokopiou, a 32-year-old actress performing for the third time, summoned the sacred light of Apollo, with the help of a parabolic polished metal mirror.
A number of bomb alerts have hit European countries since the devastating Madrid train bombings on March 11.
False bomb alerts in train stations in Amsterdam and near the border with Belgium on Thursday severely disrupted train services in the Netherlands.
French railway officials said on Wednesday they had neutralized a bomb containing several detonators found on a rail line linking Paris to the Swiss city of Basel.