Japanese police have carried out raids at 11 locations linked to North Korean institutions in Japan. Authorities are focusing on two shadowy groups that some Korea-watchers contend are front organizations engaged in technical and scientific espionage for Pyongyang.

The offices of two organizations with close ties to communist North Korea were targets of searches Friday led by the Tokyo Metropolitan Police Department's Public Security Bureau.

At one of the offices, staff shouted at and jostled with police officers for 20 minutes before investigators could make their way inside.

Police say the catalyst for the raids were products sold over the Internet that were advertised as cures for cancer and AIDS. Japanese media on Saturday quote investigators saying a main ingredient of the touted miracle cures was ginseng, a popular Korean health supplement.

The two main organizations raided were the Korean Association of Science and Technology in Japan, known by the acronym Kakkyo, and the Kim Man Yu science promotion council, which runs a hospital in Tokyo and another in Pyongyang.

Both organizations are under the umbrella of the pro-Pyongyang General Association of Korean Residents in Japan, known as Chongryon in Korean. That association serves as North Korea's de facto embassy in Japan as there are no diplomatic relations between Tokyo and Pyongyang.

The Japan raids came amid investigations of alleged North Korean involvement in counterfeiting of U.S. dollars in the United States and Northern Ireland, drug smuggling in Australia and money laundering in Macau.

Northeast Asia policy analyst Balbina Hwang at the Heritage Foundation in Washington believes the timing of the Tokyo raids was no coincidence.

"I think it is very carefully coordinated among the governments and it is absolutely no coincidence, especially given that the United States and other countries have expressed their desire that they will continue to pressure North Korea about all these activities, coincidental with the diplomatic initiative about the nuclear program," said Balbina Hwang.

The two Koreas, the United States, China, Russia and Japan agreed last month to hold a fifth round of talks in Beijing in November aimed at ending Pyongyang's nuclear weapons programs.

Some experts have said the two scientific groups have long been suspected of acquiring and transferring missile, nuclear and other technology from industrialized nations to North Korea.

Japanese media reports say two men were arrested in Tokyo on suspicion of violating the Pharmaceutical Affairs Law. Both are reported to be vice presidents of Kakkyo.

Japan is home to an estimated 600,000 ethnic Koreans. No more than one third are affiliated with the pro-Pyongyang organization. But their monetary remittances to North Korea, much of it from the pachinko (pinball) industry, have been a major source of hard currency for Pyongyang.