BELGRADE, Serbia — Pavle Mircov and his partner, Daniella, nervously scan their e-mail in-box every 15 minutes, desperate for economic salvation: a buyer willing to pay nearly $40,000 for one of their kidneys.

The couple, the parents of two teenagers, put their organs up for sale on a local online classified site six months ago after Mr. Mircov, 50, lost his job at a meat factory here. He has not been able to find any work, he said, so he has grown desperate. When his father recently died, Mr. Mircov could not afford a tombstone. The telephone service has been cut off. One meal a day of bread and salami is the family’s only extravagance.

“When you need to put food on the table, selling a kidney doesn’t seem like much of a sacrifice,” Mr. Mircov said.

Facing grinding poverty, some Europeans are seeking to sell their kidneys, lungs, bone marrow or corneas, experts say. This phenomenon is relatively new in Serbia, a nation that has been battered by war and is grappling with the financial crisis that has swept the Continent. The spread of illegal organ sales into Europe, where they are gaining momentum, has been abetted by the Internet, a global shortage of organs for transplants and, in some cases, unscrupulous traffickers ready to exploit the economic misery.