BURGAS, Bulgaria — The attack on a tour bus carrying Israeli vacationers outside the airport here was carried out by a suicide bomber carrying a fake American identification, officials said on Thursday.

Seven people, including six Israelis, were killed along with the bomber when the bus exploded in a fireball on Wednesday and dozens more were injured in what Bulgaria, Israel and the United States called a terrorist bomb attack. Israel quickly blamed Iran and promised a firm response. There was no immediate claim of responsibility.

Speaking to reporters at the airport on Thursday morning, Interior Minister Tsvetan Tsvetanov said that the death toll stood at eight people, including the bomber, who was carrying a fake Michigan driver’s license at the time of the blast. Six Israelis died, one overnight, as well as the 36-year-old Bulgarian bus driver.

Mr. Tsvetanov described the bomber as a man with long hair wearing a backpack. The man looked like a tourist and blended in with the travelers from Israel as he placed the backpack in the bus’s baggage compartment before it exploded, security footage showed.
According to a statement Thursday on the Interior Ministry Web site, the police presence in Burgas has been increased and security raised at the hotels where Israeli tourists are staying.

The airport remained closed on Friday, with flights redirected to Varna. About 64 Israeli tourists remained at the airport, where they were being cared for by the Bulgarian Red Cross.

Photographs and video taken at the airport showed billowing black smoke from the explosion that left the bus a blackened skeleton, scorched several buses nearby, shattered windows and forced the airport to temporarily close. Witnesses quoted by Israeli news media said some victims were on fire as they tried to escape the bus. They said that many suffered severe burns and that body parts were flung around the parking lot.
Iran had no immediate official comment on Israel’s accusations but news agencies quoted state television as rejecting the accusation.

No group claimed responsibility for the blast, which the Bulgarian foreign minister said had been caused by a bomb placed in the bus’s luggage compartment. But if the Israeli accusations are confirmed, the blast would be the first successful attempt by Iranian operatives to kill Israelis in attacks abroad after a string of failed bomb plots targeting Israeli diplomats in Georgia, India and Thailand this year.

Even without such confirmation, the Bulgarian explosion escalated the tensions between Israel and Iran that are already high because of the Iranian nuclear energy program, which Israel has called a guise for Iran to develop nuclear weapons despite Tehran’s repeated denials.

The explosion came only a few days after a suspected operative of Hezbollah, the Lebanese militant group with close ties to Iran, was arrested in Cyprus on suspicion of plotting to kill Israeli tourists there. That was big news in Israel and reinforced the sense of suspicion that Israelis vacationing abroad might be targets.

Still, the deputy foreign minister of Israel, Danny Ayalon, was quoted on Israel’s Channel 2 television as saying there was no warning of the Bulgaria attack.

In the capital, Sofia, home to most of the 5,000 Bulgarian Jews in the overwhelmingly Christian country of more than seven million, the mayor ordered police deployments in all public places linked to the Jewish community, The Associated Press reported.

In Washington, President Obama said in a statement that he strongly condemned “today’s barbaric terrorist attack on Israelis in Bulgaria,” but he did not specifically accuse Iran.

In what appeared to be an Obama administration effort to reinforce his support for Israel, which Mr. Obama’s Republican adversary, Mitt Romney, has called into question, the White House also said in a separate statement that Mr. Obama had called Prime Minister Benjamin Netanyahu to offer his condolences, and had “pledged to stand with Israel in this difficult time, and provide whatever assistance is necessary to identify and bring to justice the perpetrators.”

The Bulgarian Foreign Ministry said Wednesday 30 had been wounded. At least four victims suffered burns and shrapnel wounds, a local hospital official said.

Mr. Netanyahu convened security consultations after the bus explosion, which he called a “terror attack in Bulgaria.”

“All signs point to Iran,” Mr. Netanyahu said in a statement. He and other Israeli officials noted that the explosion came on the 18th anniversary of a bombing of an Argentine Jewish center in Buenos Aires that killed 85 people and wounded hundreds, an attack for which Argentine prosecutors have blamed Iran.

Bellicose adversaries, Israel and Iran have a long history of accusing each other of terrorist attacks. Iran, which does not recognize Israel’s right to exist and has sometimes referred to Israel as a Zionist plague on the Middle East, has blamed Israeli agents for a string of assassinations of Iranian nuclear scientists over the past five years, for which Iran has vowed revenge.

Israel has never confirmed or denied responsibility for those assassinations.

Mr. Netanyahu’s statement recalled what Israel has described as Iranian plots to target Israelis in Thailand, India, Georgia, Kenya, Cyprus and other countries. He called such a pattern a “global Iranian terror onslaught, and Israel will react firmly to it.”

Burgas, on the Black Sea, is a popular destination for Israelis. The explosion occurred outside the terminal shortly after the victims arrived via a charter flight from Tel Aviv with 154 people, including eight children.

“We were just getting on the bus when suddenly someone came near the bus’s front door and exploded,” Gal Malka told an Israeli television station. “We heard a boom and next thing we saw were body parts scattered on the ground. There were wounded people also on the ground. I could see a burned hole in the side of the bus.”

Oren Katz described tamping down the flames of a woman who had caught fire. “It was strange that there were so many security people around but none of them seemed to be focused on actually helping the wounded people, and couldn’t believe that I of all people was the one taking care of this burning woman and stopping her from burning up.”

A spokesman for Israel’s private search and rescue organization, ZAKA, said it was preparing to send a team to Bulgaria to collect body parts for identification and proper Jewish burial.

Burgas is 250 miles east of Sofia. In recent years Burgas has become popular as an inexpensive destination for groups of Israeli teenagers taking trips after finishing high school and before their military service.

Some Iran analysts in Israel counseled caution about assigning responsibility for the Bulgaria blast until more evidence was presented. “It’s far too early to conclude who was behind the bombing in Bulgaria today,” said Meir Javedanfar, an Iran expert at the Interdisciplinary Center in Herzliya, Israel. “For now all we have to go on are assumptions, and a list of credible suspects.”

He did not rule out Al Qaeda, recalling the deadly attack on Israeli tourists at a hotel in Mombasa, Kenya, in 2002.

But others gave credence to Mr. Netanyahu’s suspicions, including some Iranian experts who have criticized his policies toward Iran. “Though no evidence has been presented, he may not be wrong. The government in Tehran is a very likely suspect,” said Trita Parsi, founder and president of the National Iranian American Council, in a column published by The Daily Beast Web site.

Having failed to carry out bombings of harder Israeli targets like diplomats, Mr. Parsi wrote, “it appears that Tehran has shifted its focus to softer targets. Targeting unwitting tourists is much easier than security-conscious officials. If this is the case, the ongoing dirty war between Israel and Iran may be getting out of control.”