Customs officials have banned exports of blood samples and other biological materials from Russia, leading courier companies said Wednesday, a decision that experts said could lead to the deaths of patients in need of bone marrow transplants and other treatment.

The Federal Customs Service declined to comment, but the Health Ministry said in a statement the decision by customs' officials concerned only major shipments of biological materials and would not affect ordinary patients.

Representatives of couriers DHL and TNT-Express, however, told The Associated Press that customs officials on Tuesday ordered exports of all biological materials halted without explanation.

The Health Ministry and other Russian officials gave no reason for the decision, which appeared to reflect official suspicions about Western companies' involvement in the sensitive sphere of health care amid a deepening chill in ties and accusations of European and U.S. meddling in Russia's affairs.

Doctors and health experts warned the ban could cost patients waiting for bone marrow transplants their lives, saying Russia maintains a very small bank of such donors and most patients send their blood samples abroad to find a donor there.

"Children who need bone marrow transplants will die as a result of this," said Vadim Gorodetsky, deputy head of the Russian Academy of Sciences' Hematology Research Center. "Even if one person dies because of this ridiculous decision, those who ordered this should go to prison."

Experts said the measure would also seriously hamper medical and pharmaceutical research in Russia, because it would prevent sending samples and results of clinical trials abroad.

The Russian daily Kommersant speculated in its Wednesday issue that the decision could be linked to the Kremlin's concept of fighting biological terrorism dating back to 2004 and official concerns that foreign pharmaceutical companies were testing potentially harmful medicines on Russians.

Russian officials have repeatedly expressed concern that foreign pharmaceutical companies were conducting dangerous clinical trials on Russian patients, even though no foreign medicine could be sold in Russia without first undergoing clinical trials in the country.

Citing an unidentified medical source, Kommersant said the move came after Nikolai Patrushev, head of the Federal Security Service, the top KGB successor agency, presented a report on the subject to President Vladimir Putin earlier this month. The newspaper claimed the report alleged that a number of Western medical research centers were using clinical trials in Russia to prepare biological weapons that would target Russians.

That alleged report comes amid increasing strain in relations with the West and claims from Patrushev and other Russian officials that Western nations are trying to isolate and weaken Russia.

The Federal Security Service declined immediate comment.