Italian fishermen have barricaded the entrance of Lampedusa harbour with boats seized from illegal immigrants in an attempt to prevent further vessels from reaching the shore.

Protesters on and off the Mediterranean island on Monday voiced concerns about the relentless tide of North African migrants mainly fleeing unrest in Libya and Tunisia.

"Enough, we're full," read a slogan scrawled on a white sheet and carried by two protesters.

More than 3,000 new migrants have arrived in the last three days alone on the island of 5,000 residents, which lives off tourism and fishing.

The shelters on the island are full and migrants have taken to sleeping on the docks or in makeshift tent camps in fields.

More than 15,000 migrants have arrived since mid-January, when Tunisians overthrew Zine El Abidine Ben Ali, the longtime former president.

Symbolic protest

Monday's blockade was a mostly symbolic act, since few migrants' boats have entered the small port or docked by themselves at Lampedusa.

The migrants' boats, mainly open-topped wooden fishing vessels purchased from smugglers, are spotted far offshore by Italian coast guard air and sea patrols, whose motorboats then escort them to Lampedusa.

With Lampedusa overwhelmed, some migrant boats are being diverted to Linosa, another tiny Italian island in the archipelago.

Boatloads of migrants have also reached small Mediterranean island of Malta.

Italy has promised to increase in the coming days the number of naval transport ships assigned to transfer the migrants from Lampedusa to detention centres elsewhere.

The government of Silvio Berlusconi, Italy's prime minster, has offered the equivalent of $281m in aid and credit lines to Tunisia to help tighten border controls.

Source: Agencies