SOFIA, June 5 (Reuters) - Bulgaria said on Wednesday it only had an "indication" that Lebanon's Hezbollah might have been behind a deadly bus bombing in July and that this alone did not justify any European Union move to list it as a terrorist group.

The new Socialist-led government backed away from charges by its centre-right predecessor that the Shi'ite Muslim militant group had carried out the attack that killed five Israelis and their Bulgarian bus driver in the Black Sea city of Burgas.

"It is important that the (EU) decision be based not only on the bombing in Burgas because I think the evidence we have is not explicit," Foreign Minister Kristian Vigenin, whose government took office last week, told national state radio BNR.

"There is an indication that it is possible (that Hezbollah was behind it) but we cannot take decisions with important consequences for the EU based on indirect data.

"If we have enough serious proof from other cases, then we will not waver to back such a decision," Vigenin said.

Hezbollah has denied any involvement in the Burgas bombing.

Vigenin said the Bulgarian authorities were pursuing their inquiry into the attack and would keep EU governments informed.

A British request to blacklist Hezbollah ran into opposition in the EU on Tuesday, with several governments voicing concern that doing this would increase instability in the Middle East.

Some diplomats have said that such a move would complicate the EU's contacts with Lebanon, where Hezbollah is part of the coalition government, and could increase turmoil in a country already suffering a spillover of civil war from Syria

Britain, which has in the past held contacts with what it calls Hezbollah's "political wing" has argued that the group should face European sanctions because of its involvement in the Burgas bombing and a plot to attack Israeli interests in Cyprus.

Blacklisting Hezbollah would mark a major policy shift for the EU, which has resisted pressure from Israel and Washington to do so for years.

In February, the previous Bulgarian cabinet, a staunch ally of Washington, urged European governments to take a harder stance towards Hezbollah after blaming it for the Burgas attack.

The Socialists, then in opposition, accused the centre-right government of rushing to implicate Hezbollah without proof and exposing the Balkan country to possible new terrorist attacks.

EU governments will again discuss the proposal to blacklist Hezbollah later this month. (Reporting by Tsvetelia Tsolova; Editing by Alistair Lyon)

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