ROME (AFP) - Thirteen asylum-seekers drowned on Monday while attempting to swim ashore after their vessel ran aground off Italy's coast, the local mayor said.

"There were 13 dead. Some people were saved and sent to nearby hospitals," Mr Franco Susino, the mayor of Scicli in southeast Sicily near where the incident happened, said on the news channel SkyTG24.

"We did what we could to save human lives. Some tourists raised the alarm and helped out," he said, adding he believed the migrants had been thrown overboard by crew members.

"These people are treated like animals," he said.

SkyTG24 and the ANSA news agency said there were between 150 and 200 people packed on the boat and Susino said most of them were from Eritrea.

Ansa said two suspected crew members have been arrested under an Italian law against people who facilitate illegal immigration.

A swimmer had warned coast guards after seeing a small abandoned boat in poor condition near the shore.

The coastguards are continuing to search the maritime zone around the boat and divers are looking for any other victims.

In a similar incident in Catania in another part of Sicily in August, six young Egyptians drowned trying to reach the shore.

The victims had jumped from the trawler thinking they had arrived onshore when in fact they were some 15m away.

Since the start of the year over 22,000 immigrants have reached the southern coast of Italy, three times more than the total number last year.