A Scandinavian trawler has set sail from Sicily as part of a two-month mobilisation to break the nine-year Israeli siege of the Gaza Strip.
It joined three other boats (Rachel, Vittorio and Juliano II) departing from Crete in Greece.
Unidentified military vessels and reconnaissance fighters hovered briefly over the Swedish trawler on Saturday afternoon before disappearing, Gaza website reported, quoting the Scandinavian trawler captain Joel Opperdoes Marianne.
An Israeli naval and land blockade has restricted the movement of 1.8 million Palestinians and goods from and to the Gaza Strip since the Islamist Hamas movement won parliamentary elections and became its de-facto ruler in 2006, inflicting increasing hardship on the impoverished population.
Marianne, the Scandinavian trawler carrying medical equipment and solar panels, set off in May to Gaza, stopping at Sicily in Italy, Helsingborg in Sweden, Copenhagen in Denmark, Galicia in Spain, and Lisbon in Portugal.
The flotilla is currently sailing towards the southeast part of the Mediterranean and is expected to arrive in Israeli waters in the next few days.
The first attempt to break the siege with a flotilla was organised in 2010. Israeli forces raided the ships in international waters, killing nine activists and injuring dozens of others on the Turkish ship Mavi Marmara. A second attempt was organised out of Greece in 2011, but the vessels were turned back by the Greek coastguard.
In response to news of the Marianne setting sail for Gaza, Israel announced in May that it would not allow unauthorised ships to enter its territorial waters, Israeli daily The Jerusalem Post reported.
Israeli foreign ministry spokesman Emmanuel Nachshon called the flotilla an "unnecessary provocation."
An Arab Israeli MP, Basel Ghattas, announced last week that he would join the flotilla to break the siege, causing outrage in Israel.
Tunisia's former president Moncef Marzouki is also on board, among 50 human rights activists and politicians from around the world heading to the besieged Gaza with the flotilla. Members of parliament from Spain, Jordan, Greece and Algeria have also joined the flotilla with members of the European Parliament.
To follow latest updates on the route of Flotilla III, readers can log on to the Ship to Gaza interactive blog.