Dawn.com says "“The agents explained to them that they had to leave because of strong political pressure on Bulgaria from Israel,” he said, adding that they had departed for Istanbul." and the Sofia Globe says "It emerged that the three Palestinians were in Bulgaria at the invitation of the Centre for Middle Eastern Studies – an entity, to put it mildly, that generally serves as a platform for anti-Israel views." and "Reports quoted the Hamas group as saying that they came to Bulgaria to present the “Palestinian narrative and expose the false Israeli narrative on the Palestinians and Hamas”."
2 Turkish security personnel killed, 24 wounded by Kurdish suicide bomb in eastern Turkey (Reuters)
from the article: Bulgaria expels 3 Hamas lawmakers