Bulgarian postal services have been put on red alert after Sofia police intercepted a suspicious package addressed to the Israeli Embassy in the capital.

The postal departments have been asked to screen arriving parcels and the officials to be extra vigilant while handling them.

"This is the highest level of alert and security in the postal offices. Emergency situations call for emergency measures," Transport Minister Alexander Tsvetkov commented.

Earlier this week Greek police carried out a controlled explosion on a package found outside Parliament and two more at the Russian and Bulgarian embassies.

And two other packages were intercepted at the Chilean embassy and the offices of a courier company.

Police spokesman Athanassios Kokalakis said an object was thrown into the Swiss embassy courtyard and a "deafening blast" was heard, but no one was injured.

A suspicious package was also discovered at the offices of German Chancellor Angela Merkel in Berlin.