The Foreign Ministry issued a travel warning on Thursday for Israelis traveling in Japan, recommending that they leave the quake-stricken country immediately due to possible radiation leaks.
Meanwhile, a Swedish official says low concentrations of radioactive particles are heading eastwards from Japan's disaster-hit nuclear power plant and are set to reach North America in days.
"Israelis are advised to leave Tokyo towards the south and even to consider departing from the country entirely," the Foreign Ministry stated. Citizens were also advised to refrain from traveling to Japan "until the situation becomes clear".
The embassy in Tokyo remains open, however, and Israelis who remain in the country are being advised to stay in touch with it.
The warning from Lars-Erik De Geer, research director at the Swedish Defence Research Institute, a government agency, cites data from a network of international monitoring stations established to detect signs of any nuclear weapons tests.
Stressing that the levels were not dangerous for people, he predicted the particles would continue across the Atlantic and eventually also reach Europe.
"It is not something you see normally," he said by phone from Stockholm. But, "it is not high from any danger point of view."
He said he was convinced it would eventually be detected over the whole northern hemisphere.
"It is only a question of very, very low activities so it is nothing for people to worry about," De Geer said.
"In the past when they had nuclear weapons tests in China ... then there were similar clouds all the time without anybody caring about it at all," he said.
Before he spoke, the US Nuclear Regulatory Commission advised any Americans living near Japan's crippled Fukushima nuclear plant to move at least 80 km away but it played down the risks of contamination to the United States.
"All the available information continues to indicate Hawaii, Alaska, the US Territories and the US West Coast are not expected to experience any harmful levels of radioactivity," it said in a statement on Wednesday.
Reuters contributed to this report