Bulgaria’s intelligence chief says he is taking seriously indications that terrorists may target the Nato summit in Istanbul next week and the August Olympics in Athens.
“We do have such signals, and we take them very seriously,” said General Kircho Kirov.
“We have communicated all relevant information to our colleagues in the neighbouring countries.”
Bulgaria borders both Greece and Turkey.
There is little hard evidence that al-Qaida has operatives in the region.
But most Balkan countries have lax border controls, and arms and explosives are easily bought in the region, which is home to some militants with ties to radical Islamic groups.
Other Bulgarian officials have warned of possible terror threats in the region, especially during the Athens Olympics.
Bulgaria says it will work with Greek authorities and security personnel from the US, Britain, Germany and Russia during the games.