A Portuguese "peace boat" with students and activists aboard set sail from the north Australian port of Darwin Monday for East Timor, with an Indonesian navy flotilla determined to block it.

The 540-ton converted car ferry Lusitania Expresso left in driving rain as some 140 Timorese supporters sang freedom songs and shouted independence slogans in Portuguese.The protesters want to lay wreaths at the Santa Cruz cemetery in Dili, East Timor, in memory of the 50 to 180 civilians massacred by Indonesian troops in November.

Many wore white T-shirts emblazoned "East Timor Peace Mission" in Portuguese as they crowded passageways and stood on lifeboats to wave farewell.

Indonesia has called the mission provocative and naval vessels have been massed in the Timor Sea to prevent a landing.

Organizers say they will adhere to international maritime law and halt if challenged by Indonesia.

"My main concern is the safety of the people on board of this ship," Capt. Luis dos Santos told reporters. "At the time, I will act accordingly to fulfill my responsibilities."

Asked whether he would try to run an Indonesian blockade, Capt. dos Santos said: "Probably not. When it's brute force against me, and the ship is civilian and I have no arms, I have no choice but to turn around."

Indonesia invaded the former Portuguese colony of East Timor in 1975, annexing it the following year in a move not recognized by the United Nations.

Some 15 passengers quit the protest voyage before the ship sailed, citing job and study demands.

"Some people had to go because of exams, because of their jobs," Belgian medical student Jean-Bertrand Christaensen, 24, said as he prepared to go home.

"It was hard. I was very eager to go on board," he said, waving to his friends from the wharf.

Among the 50 journalists aboard was correspondent Dewi Anggraeni Fraser of Indonesia's Tempo weekly news magazine.

Asked about statements from Jakarta that any Indonesian journalist aboard the ferry would be considered a traitor, Anggraeni Fraser said she felt uneasy but that her editors had cleared her coverage of the mission.

"It feels a bit scary," she said. "I can't see why I shouldn't go. I don't believe the Indonesian government is a primitive government that cannot see the difference between covering this in a professional capacity and participating."

After some delay, the ferry slid away with a blast of its horn just after sunset. The crowd clapped and waved while some shouted, "The battle continues! Viva East Timor!"

After some delay, the ferry slid away with a blast of its horn just after sunset. The crowd clapped and waved while some shouted "The battle continues! Viva East Timor!"

Participants from 19 countries have joined the protest voyage.