Israeli Tourism Minister Stas Misezhnikov paid tribute at Sofia's grand synagogue to the six victims of last week's suicide bombing during his visit to Bulgaria Monday, while also meeting the prime minister.

"Bulgaria and Israel are friends and we will not let this terrorist act cast a shadow over our traditionally good relations," Misezhnikov said after talks with Boyko Borisov, according to a statement.

"Any negative change in our relations would be to give in to terrorism."

"Israeli tourists are important for us," said Borisov. "But not really for economic reasons but because for them Bulgaria is like a second country and they feel comfortable here."

Misezhnikov was due to attend on Tuesday a ceremony in Burgas on the Black Sea, a popular destination for Israeli tourists, to commemorate the victims of Wednesday's attack, five Israelis and one Bulgarian.

Bulgarian investigators, helped by international counterparts, were still trying on Monday to identify the suicide bomber. Israel has blamed Iran and Lebanese militia Hezbollah for the bombing. Iran has denied any involvement.

Bulgarian media reported later on Monday, quoting anonymous sources, that the bomber entered the country from neighbouring Romania, spoke Russian and was accompanied by a woman.

Private television bTV reported that investigators have recovered what it called the bomber's "biological traces" from a hotel in Varna, further up the Black Sea coast from Burgas, where the bomber stayed two days before the attack.

The Trud daily meanwhile quoted a taxi driver who was alleged to have driven the bomber the day before the attack saying that the man spoke Russian well.