Israeli navy on Sunday night sighted the pro-Palestinian "Freedom Flotilla" bound for the Gaza Strip and ordered the convoy to dock at an Israeli harbor, unveiling what could be a showdown between Israel and peace activists.

Israeli navy vessels spotted and made contact with the Gaza aid ships, which were more than 200 km off the Palestinian enclave late Sunday night, reported local daily The Jerusalem Post.

The convoy were asked to follow the navy boats to dock at Ashdod port near Tel Aviv, or else the navy will board the activists' ships, said the report.

Three missile boats left northern Israel's Haifa naval base earlier Sunday night, planning to intercept the convoy.

The Gaza aid ships set sail on Sunday from the Mediterranean international waters near Cyprus and headed to the besieged territory amid tension due to Israel's threats to block the convoy.

The six-vessel flotilla, aiming at focusing world attention on the plight of the Gazans, carries more than 10,000 tons of aid, stationery, medical supplies and construction materials as well as hundreds of peace activists from over 40 countries.

Israel imposes a tight blockade on the coastal enclave since the Islamic Hamas movement forcibly seized the territory in 2007 after routing rival Fatah party which now rules the West Bank.