Hundreds of activists at sea in the eastern Mediterranean were determined on Saturday to break Israel's Gaza blockade after their boats were "tampered with," an organiser of the aid operation said.
Israel, which has branded the operation illegal, has warned that its navy will intercept the vessels.
"We are more determined than ever. These actions can be frustrating but in the end they are not going to stop us," Elize Ernshire of the Free Gaza Movement which organised the flotilla said.
Ernshire said two of the seven boats in the humanitarian aid operation had been "tampered with," forcing one to drop out and the other to pull into port in Turkish-held northern Cyprus for repairs.
"These boats had no previous mechanical problems and had undergone full (mechanical) surveys," Ernshire said, declining to elaborate on the damage. A statement would be issued at a later date.
One of the damaged boats transferred its passengers at sea, while the other pulled into Famagusta in the Turkish-held sector of the divided island and was expected to head back out to rejoin the flotilla.
She said the flotilla of cargo and passenger ships was located 120 nautical miles from the Gaza coast and would head off toward the Palestinian territory late on Saturday, aiming to arrive at around noon (0900 GMT) on Sunday.
Five European MPs are among the activists, she said. However, another five would not be on the boats that had been due to leave on Friday but were delayed due to a lack of cooperation by Greek Cypriot authorities.
Organisers had been kept "under close scrutiny" while on land in Cyprus by helicopters and intelligence agents, she added. "For a humanitarian operation, this was a real eye opener."
The six remaining boats in the flotilla regrouped in international waters are loaded with thousands of tonnes of supplies. Organisers said an eighth ship, which left from Ireland, would travel toward Gaza separately.
"The Cypriot government does not want us to leave from Cyprus. I can only assume pressure was put on them," said Audrey Bomse, another member of the Free Gaza Movement.
A Cypriot government official said Nicosia had not received any formal request from the Palestinian Authority for humanitarian aid and that it was not in the divided island's interests to assist the operation.
Bomse said the involvement of Famagusta had led to the withdrawal of Greek and Greek Cypriot politicians from the operation, but MPs from Ireland, Italy, Sweden, Norway and Bulgaria were still involved.
Greece and Cyprus regard the self-proclaimed Turkish Republic of Northern Cyprus, where Famagusta is the main port, as an illegal entity.
Earlier this week, Israel told the ambassadors of Cyprus, Turkey, Greece and Ireland -- the countries from which the ships set sail -- that the flotilla would be breaking international law.
With its naval forces at the ready, the Jewish state plans to intercept the vessels and detain the hundreds of people aboard in the Israeli port of Ashdod before deporting them.
Organisers dismissed the Israeli charge that their blockade-busting bid is illegal.
"Most despicably of all, Israel claims that we are violating international law by sailing unarmed ships carrying humanitarian aid to a people desperately in need," the Free Gaza Movement said.
Israel imposed a crippling blockade on Gaza in 2007 after Hamas -- an Islamist movement committed to the destruction of Israel -- seized power in the impoverished, overcrowded Palestinian territory.
Because of the blockade, only limited reconstruction has been possible in the wake of a devastating 22-day offensive Israel launched on December 27, 2008.
Pro-Palestinian activists have landed in Gaza five times, with another three attempts unsuccessful since their first such sea voyage in August 2008.
To date, the aid has been largely symbolic, but organisers say the flotilla now under way is laden with 10,000 tonnes of aid, ranging from pre-fabricated homes to pencils.