Israeli Prime Minister Benjamin Netanyahu accused Iran today of being the most irresponsible country in the world and said sanctions against Tehran over its nuclear programme "haven't worked."

"Iran has been exposed for being the most irresponsible power on earth today. 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.

"For such a regime to have nuclear weapons is something of enormous concern for the United States and for Israel," he said.

He was speaking after Israel accused Iran of unleashing a terror campaign in world capitals following three explosions in Bangkok on Tuesday and attacks on Israeli embassy staff in India and Georgia on Monday.

Thailand on Wednesday charged two Iranians in what Thai intelligence officials said was a botched attempt to attack Israeli diplomats.

The Bangkok blasts came just 24 hours after an Israeli embassy car blew up in New Delhi, seriously wounding a woman diplomat. On the same day, police in Tbilisi found another bomb attached to an embassy car which was defused before it could detonate.

"This regime was born taking over an embassy, it's now attacking diplomats far and wide," Netanyahu said, referring to the storming of the US embassy in Tehran in 1979.

He said the Jewish state had information "of an ongoing effort, an attempt by Iran to conduct terrorism in many parts of the world. Happily so far this has not caused any loss of life."

"I think the US and any other responsible country in the world ought to be concerned about the pursuit of nuclear weapons by Iran," he said a day after President Mahmoud Ahmadinejad unveiled what was billed as its first domestically produced 20-percent enriched uranium.

Iran has been slapped with four sets of UN sanctions and a raft of unilateral US and EU sanctions designed to halt a programme the West fears masks a drive for atomic weapons.

Tehran denies this charge, saying its nuclear programme is entirely peaceful.

"I hope sanctions work, but so far they haven't worked and we've been seeing a regime that breaks all the rules. They have absolutely no respect for international norms," Netanyahu said.

"They send children into minefields, they blow up airplanes, they have suicide bombers, they send tens of thousands of rockets to our cities and our towns," the Israeli premier said.

"Such a regime obviously should not have atomic bombs and I believe the international community is becoming aware by day of what it means to have Iran continue its programmes."

Earlier, Israeli Defence Minister Ehud Barak echoed Netahyahu's comments on sanctions.

"These (current) sanctions ... might not suffice to compel the Iranian leadership to take decisions so we feel that there is still a need for more effective and paralysing sanctions on Iran," Japan's Kyodo news agency quoted him after a meeting with his Japanese counterpart Naoki Tanaka.

But Barak also accused Tehran of "exaggerating" progress in its nuclear programme.

"The Iranians are continuing to progress but what they presented yesterday was a show. There are many things which have been presented in an exaggerated manner, partly to dissuade the world from going after them," he told Israeli public radio by telephone from Tokyo.

Iran also said on Wednesday it had installed another 3,000 centrifuges to increase its uranium enrichment abilities and was stepping up exploration and processing of uranium yellowcake.

"The Iranians are boasting of successes they have not achieved and they still have much to do to reach the second or third generation of centrifuges," Barak said.

"The Iranians want to give the impression they were more advanced to create the impression that they have passed the 'point of no return' -- which is not true."

The fact that Iran had moved some of its enrichment facilities into an underground site was aimed at making it more difficult to carry out "surgical strikes" to halt it, Barak said.

In recent weeks, there has been feverish speculation that Israel was getting closer to mounting a pre-emptive strike on Iran's nuclear programme, but last month, Barak said such a decision was "very far away."

On Wednesday, Japan urged Israel not to take military action against Iran, with Prime Minister Yoshihiko Noda warning Barak that a military strike could be "extremely dangerous," Japan's Kyodo news agency reported.

But Barak refused to confirm details of his talks with the Japanese premier, saying only: "The Japanese now understand much better the situation."