Police in Thailand said on Friday they were hunting for a fifth Iranian suspected in a failed bomb plot in Bangkok that has sent tensions between Israel and Iran soaring.

The tourist magnet has stepped up security following Tuesday's blasts, the third bomb incident to shake world capitals in less than 24 hours. Teheran has denied Israeli charges it is waging a terror campaign against the Jewish state.

An airport security officer talks to a tourist during a patrol at Suvarnabhumi Airport in Bangkok, on Friday. Thai police said they are searching for two more suspects, including a possible explosives specialist, in a botched terror plot against Israeli diplomats that has been blamed on Iran. [Photo/Agencies]

Arrest warrants have been issued for four Iranians, two of whom have been detained and charged over the botched attack, which came to light after an apparently unintended explosion at a Bangkok house on Tuesday.

Now police are compiling evidence and witness accounts to seek a warrant for another suspect whose whereabouts are unknown.

"The additional suspect is 52-year-old Iranian man Nikkhahfard Javad who was seen leaving the house hours before the blast," said Bangkok Metropolitan Police deputy commander Anuchai Lekbumrung.

According to Thai media, the man is suspected of being a trainer in bomb making.

Thai Police Chief Phrewphan Damapong has said that Israeli diplomats were the intended target of the plot, but Teheran has rejected accusations that it is behind a terror campaign against the Jewish state.

One of the suspects - 28-year-old Saeid Moradi - had his legs blown off as he hurled a bomb at Thai police while fleeing.

Another, Mohamad Khazaei, was detained trying to board a flight out of the country.

Thailand is seeking the extradition of another Iranian arrested in Malaysia in connection with the blasts, while an Iranian woman who rented the house used by the suspects in Bangkok is thought to have fled the kingdom.

Israel has blamed Iran over the Bangkok plot, as well as attacks on Israeli embassy employees in India and Georgia on Monday.

Israeli Prime Minister Benjamin Netanyahu accused Teheran on Thursday of being "the most irresponsible power on Earth" and said sanctions over its nuclear program "haven't worked".

"The one that exports terror with abandon is murdering people and breaking all the rules," Netanyahu told reporters during a one-day visit to Cyprus.

Teheran has denied responsibility for the string of incidents.

Bangkok has been on alert since mid-January when police arrested a Lebanese man with alleged links to Hezbollah on suspicion he was planning an attack, following a US warning that tourists might be targeted.

Hezbollah chief Hassan Nasrallah denied his Lebanese militant party had any role in the attacks on Israeli diplomats, in a televised address on Thursday.

US Ambassador Kristie Kenney told AFP that the US warning for Bangkok was still in effect.

"We really can't say at this point while it is being investigated when the threat will be over," she said.

Meanwhile, it emerged that three of the suspects holidayed in the Thai resort of Pattaya just days before the blasts.

"The three suspects stayed in different hotels in Pattaya," said an immigration officer in the coastal city who did not want to be named.

Police have tracked down a Thai woman known as "Nancy" who escorted one of the men, Mohamad Khazaei, during his stay, he added.

"The most important evidence we found are pictures in Nancy's mobile phone taken on the night of Feb 11, which prove that these suspects know each other," the officer said.

Pattaya, about a two-hour drive southeast of Bangkok, has earned a reputation for its wild nightlife thanks to its thriving red light district.

According to the Bangkok Post daily, the Thai woman was also in the suspect's hotel room "but didn't detect any irregularities except one time when he barred her from approaching a closet in the room".