A previously unknown terrorist group claimed responsibility Saturday for the terror attack against an Israeli tour bus in Burgas last week while Bulgarian security authorities were reportedly searching for additional suspects involved in the bombing.Five Israelis and a Bulgarian driver were killed in the attack and dozens more were injured. Israel and the United States have accused Hezbollah of perpetrating the attack but on Saturday a group called “Base of Jihad” claimed responsibility for the attack. Bulgarian police have published pictures of the suspected bomber who was carrying forged US identification and has yet to be identified.“With Allah’s help and after close surveillance one of us succeeded in blowing up a Jewish bus in Bulgaria,” the group said in a statement that appeared on a Lebanese news site. The previously-unknown group could be connected to global jihad or being used as a cover by Hezbollah.Bulgaria's Focus News Agency quoted a spokesperson of the country's foreign ministry as denying that the group carried out the attack.Foreign Minister Avigdor Liberman said last week that Israel had solid evidence that Hezbollah, in "close cooperation with the Iranian Revolutionary Guards", was responsible for the attack.Meanwhile Saturday, the investigation into the bombing continued with Bulgarian, Israeli and American cooperation. Interpol is also said to be playing an active role in the probe. CNN reported Saturday that eyewitnesses identified a second suspect who might have assisted the bomber and described him as having short hair and speaking English with a “distinct” accent.This would be a different man than the one shown in the photos and video released by Bulgarian authorities. That man has long hair. According to the report, the second suspect might be American. On Friday, Bulgarian Police began distributing a sketch of the alleged accomplice in hopes that the public could help them in the investigation.Bulgarian investigators said on Friday that they had managed to obtain DNA samples from the fingers of the bomber and were checking databases in an attempt to identify him. Bulgarian Prime Minister Boiko Borisov told parliament he hoped that would be done in 3-4 days.Defense Minister Ehud Barak said on Friday that Israel was certain that the attack was carried out by Hezbollah. Defense officials said that it was possible that the cell behind the attack crossed into Bulgaria from Turkey or even consisted of local Muslims who were recruited into the Lebanese-based organization.“It is clear that Hezbollah is behind the attack as part of the series of events that we have seen over the past few weeks and months,” Barak said. “At the same time we do not know who the bomber is but we can tell that he looks European.”Barak also rejected claims that the attack represented an intelligence failure for Israel. "There is no country whose intelligence gathering capabilities have a wider range than Israel's...I don't think we have anything to apologize for," the defense minister said.Jerusalem Post Staff contributed to the report.