JERUSALEM, July 19 (Reuters) - The Israeli navy on Tuesday boarded a French yacht carrying pro-Palestinian activists intending to sail to the blockaded Gaza Strip and forced it to go to Ashdod port, a military spokeswoman said.

There were no immediate reports of any violence as the marines boarded the Dignite-AlKarama yacht in the eastern Mediterranean.

I can confirm that the yacht has been boarded and that everything went smoothly, there were no casualties, the spokeswoman said.

The 17-passenger vessel had declared an Egyptian port as its destination when it left Greek waters on Sunday but then said it was redirecting towards the Palestinian enclave and was hoping to arrive by Tuesday afternoon.

It had planned to sail to the Palestinian enclave as part of a flotilla carrying activists and aid, but other vessels were grounded after berthing in Greece. Activists accused the Greek government of intervening on Israel's side.

Israel, whose marines killed nine Turkish activists when they stormed a Gaza-bound flotilla in the Mediterranean last year, had vowed to stop any new attempt to breach a naval blockade it deems necessary to prevent arms from reaching Gaza, which is ruled by the Islamist group Hamas.

Palestinians and their supporters consider the Gaza blockade illegal and say it stunts the economic development of the territory, most of whose 1.5 million residents rely on aid to survive.

(Additional reporting by Nidal al-Mughrabi in Gaza, Writing by Ori Lewis; Editing by Mark Trevelyan)