Men in moon suits have been called into action on several continents for what have so far proved false alarms.

An Israeli newspaper executive opened an envelope Tuesday filled with white powder and a note reading, "Regards from Afghanistan." In Australia, anthrax jitters emptied buildings nationwide and prompted calls for a crackdown on hoaxers. In South Korea, postal workers wore gas masks and gloves to handle international letters.

In London, 12 people were taken to a hospital as a precaution Tuesday after a suspect package was delivered to the London Stock Exchange. Police said the exchange had not been evacuated and "nobody was exhibiting any ill effects."

Health authorities said the package showed no traces of anthrax.

Governments are taking the threats seriously, yet face the contradictory task of trying to raise awareness without prompting a flood of calls from a panicked public.

Italy's Health Ministry set up a hot line Monday, then appealed for people to use it responsibly after receiving 520 calls the first day, mostly from citizens afraid of anthrax or smallpox.

In many countries, postal workers are on high alert. Airlines are checking luggage and handbags ever more closely. Health ministries are stocking up on antibiotics that treat anthrax.

In Israel, a country that has endured bombings for years, citizens have been conditioned to be on the lookout for threats. Police receive hundreds of calls each day from citizens who think they've seen a suspicious package.

Maariv newspaper executive Yoram Baskind opened an envelope Tuesday with an unidentified white powder and the Hebrew-language note, "Regards from Afghanistan."

He called police who told workers to stay inside and close the windows. Hazardous materials workers rushed to the scene. Police ruled it a prank and said they may open a case against the Maariv worker allegedly involved.

In recent weeks, hundreds of thousands of Israelis have gone to government centers to pick up gas masks. The scene is reminiscent of the 1991 Gulf War, when Israelis were issued with gas masks and an antidote against nerve gas.

Since the anthrax scare began Oct. 4 in Florida, 13 people in the United States have either contracted anthrax or were exposed to anthrax spores. One person has died.

When people contract the disease, it usually responds well to antibiotics.

But with fears growing worldwide, the World Health Organization in Geneva warned people who were merely fearful of contracting the disease not to use antibiotics. The WHO said that could produce untreatable forms of anthrax.

"If people are self-medicating themselves, drug resistance _ and not only for anthrax _ could grow," said Iain Simpson, a WHO spokesman.

Anyone who feels ill should go to a doctor and should not start taking drugs independently, Simpson stressed. Different antibiotics are needed for different strains of the disease, he said.

In Canada, several buildings across the country were evacuated Monday, and parts of Parliament Hill in the capital Ottawa were closed off.

Europe has also seen a rash of suspected anthrax cases. But checks of suspicious mail in Britain, France, Sweden, and Yugoslavia all proved negative.

In Germany, the government said Tuesday that tests on a white powder found in the mailroom at Chancellor Gerhard Schroeder's offices had found no dangerous substance.

The Czech nuclear agency has sent more than 30 letters and packages for testing. Prime Minister Milos Zeman received a suspicious letter while meeting with Israeli Foreign Minister Shimon Peres, and sent it away unopened, his office said.

Fears have been surging in Asia as well.

In South Korea, postal workers are not only wearing protective gear, but are also checking incoming mail with metal detectors and X-ray machines, the Information and Communication Ministry said. The government has also allocated $53 million to fund an anti-bioterrorism task force.

In Australia, Prime Minister John Howard said the government was considering jail terms of up to 10 years for people behind a spate of anthrax hoaxes. Fifty-seven suspected anthrax cases were recorded Monday and several buildings evacuated, but no anthrax was found.

In Venezuela, health officials are testing a powder found Tuesday in an envelope sent to a Caracas woman to determine if it contains anthrax. The woman, who was not identified woman, called security officials after finding an envelope in her home mailbox that had a stamp from Florida and no return address. The woman did not open the envelope which was later found to contain a powder.