An alarming number of dead sea mammals, apparently killed on purpose by humans rather than dying of natural causes, have washed up on Greek shores in the last few weeks, marine experts said yesterday.

Theodoros Tsimbidis, the head of the Archipelagos Marine and Environmental Research Institute, told Kathimerini that between 40 and 50 protected or rare mammals had washed up over the last two months, particularly in areas of the northern and eastern Aegean.

"We have never found so many dead animals before, particularly ones that have been struck," said Tsimbidis. "Of the 10 mammals we found today, six or seven had been killed by humans."

Marine experts believe that the true number of mammals, such as dolphins or seals, that are killed is much higher as many of the animals' carcasses never reach the shore.

Tsimbidis said that it was not immediately clear what had led to so many sea creatures being found dead recently but suggested that fishermen may have killed them.