BANGKOK/LONDON - The loudest noise that Thongma Danoi had ever heard was followed 20 minutes later by the strangest sight: a dazed and bloodied Iranian carrying two wire-adorned devices through the usually sleepy Bangkok neighborhood.

"He was losing a lot of blood," said Thongma, 68, who saw the Iranian man, later identified as Saeid Moradi, fleeing a rented house blown apart by a massive explosion on Tuesday. "People were shouting, 'He's got a bomb!' I tried not to look at him."

Minutes later, he heard another explosion, as 28-year-old Moradi reportedly threw a second bomb at a taxi that wouldn't pick him up. His rampage ended nearby, outside a school, with a third explosion that ripped off one of the bomber's legs and damaged the other so badly it had to be amputated.

Israel said the Bangkok blasts were evidence of an "attempted terrorist attack" and blamed Iran. Tehran denied involvement.

As bombings go, this week's trio of apparent attempted attacks on Israeli targets -- which also included an attack on a car carrying the wife of an Israeli diplomat in New Delhi and a bomb found attached to an Israeli diplomatic vehicle in the Georgian capital Tbilisi -- seemed unusually inept.

But security experts believe they sent a clear message, the first serious retaliation for a quietly waged but increasingly bloody campaign of sabotage waged against Iran's nuclear program.

At least four Iranian nuclear scientists have been killed in recent years in attacks believed to have been carried out by or for Israel's intelligence services. While Israel invariably refuses to comment, some security analysts also suspect it has been involved in a string of major explosions at military and nuclear facilities in Iran, such as one in November that killed more than a dozen, including a senior Iranian general.

Tehran denied any involvement in this week's attacks, accusing Israel of staging them itself. But there are widespread suspicions that the real intent may have been to warn the Jewish state that Iran is prepared to retaliate in kind.

"I see in what happened a message to the effect of: 'Anything you can do, I can do too,'" said Gad Shimron, a former Mossad field officer who writes on intelligence matters. "In other words, if Israel uses terror for its security needs, it can expect reprisals from the other side."

In an environment of growing tension, paranoia and fear, there is a risk of escalation fueled by worries over Iran's nuclear program, a potential Israeli strike on Iran and a devastating wider conflict in the Gulf.

"There is more and more pressure on all sides," says Anthony Cordesman, a former senior US intelligence and defense official and now chair of strategy at the Center for Strategic and International Studies, the Washington DC-based think tank. "All of them are interacting now in ways that make it harder and harder to anticipate the actions of each other."

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