The number of victims of the attack at Burgas Airport has risen to seven, Bulgarian Foreign Ministry confirmed on Thursday, a day after the powerful blast which injured more than 30 other Israeli tourists.

Six killed, over 30 injured in bus blast in Bulgaria: foreign ministry

"This includes the Bulgarian driver of the doomed bus. Five of the victims were Israeli citizens. The seventh was likely a suicide bomber," the ministry said in a press release on its website.

On late Wednesday night, Bulgarian Prime Minister Boyko Borissov held a telephone conversation with his Israeli counterpart Benjamin Netanyahu, the ministry said.

The two prime ministers believed this attack is a threat against both countries, and expressed their sincere condolences to the relatives of the victims, the ministry added.

Bulgarian President Rosen Plevneliev on Thursday held a telephone conversation with Israeli President Shimon Peres.

According to the ministry, the main message of their conversation was that this attack cannot spoil the good relations between Bulgaria and Israel and should not be turned into a victory of terrorism over peace.

Earlier in the day, Bulgarian Interior Minister Tsvetan Tsvetanov told reporters that a suicide bomber likely carried out the bombing attack, saying that "we have established a person who was a suicide bomber in this attack. This person had a fake driving license from the United States."

An Israeli Air Force Hercules transport aircraft landed near Tel Aviv in the afternoon, after a four-hour flight ferrying 33 Israelis wounded in the suicide bombing.

Israeli side claimed that they had asked Bulgarian authorities to tighten security around tour buses carrying Israeli visitors months prior to the deadly bombing on Wednesday, the local Yediot Aharonot daily reported.

For the Bulgarian part, President Rosen Plevneliev said hours after Wednesday's attack that representatives of Israel's Mossad intelligence agency did not issue a warning at a meeting held a month ago with Bulgarian officials.

He said his country would have "acted seriously" had it been alerted to an impending terror attack.

"The attack does not mean that Bulgaria is a dangerous destination for tourists," Plevneliev said.

The tourists had arrived in Bulgaria from Tel Aviv on an Air Viva charter flight at 4:43 p.m. local time (1343 GMT) on Wednesday. One hundred and fifty four passengers, including 146 adults and eight children, were aboard the plane.

The bombing came on the 18th anniversary of an attack on a Jewish community center in Buenos Aires in 1994 that killed 85 people and wounded 300 others.

UN Secretary General Ban Ki-moon on Wednesday strongly condemned the Burgas bombing, while U.S. President Barack Obama offered condolences to the victims and pledged assistance in bringing the perpetrators to justice.

VietNamNet/Xinhuanet