Bulgaria on Friday expelled four Palestinians, including three lawmakers from Hamas, saying they had "posed a serious threat to national security".
The lawmakers had arrived in Bulgaria this week and said they would meet officials during their stay -- the first time a Hamas delegation visited an EU country since the Palestinian organisation was placed on the bloc's list of "terrorist organisations" in 2003.
Bulgaria had denied its officials were meeting with Hamas representatives and the head of the group that invited them said security agents entered their hotel rooms early Friday and took them to the airport.
"The agents explained to them that they had to leave because of strong political pressure on Bulgaria from Israel," said Mohd Abuasi, the head of the Centre for Middle East Studies.
Hamas, which rules in the Palestinian enclave Gaza, denounced the expulsion, with its spokesman Taher al-Nunu saying in Gaza City that "it reflects the extent... of Zionist pressure."
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The European Union, like the United States, considers Hamas a terror group and deals only with its rival, the Palestinian Authority.
Bulgaria's Interior Minister Tsvetan Tsvetanov defended the expulsion.
"These people came to Bulgaria with visas, but since their entry into Bulgaria, they have given different reasons for coming compared to what they had said."
The trip comes in the wake of a February 5 announcement by Sofia that the Lebanese Hezbollah -- like Hamas an enemy of Israel with strong ties to Iran -- was behind a July bombing in Bulgaria that killed five Israeli tourists and their local driver.
Last year, a Hamas delegation visited non-EU member Switzerland at the invitation of the Inter-Parliamentary Union, despite protests by Israel.