Pro-Palestinian activists say that they have lost contact with their two ships trying to break Israel's blockade of Gaza, after Israeli navy vessels reportedly intercepted them in international waters.

A spokeswoman for the activists told VOA Friday that two Israeli ships approached the boats Friday evening local time. The Israelis then asked the flotilla for its destination — to which the activists replied the “conscience of humanity” and “betterment of mankind.”

The group's spokeswoman said they lost contact with the ships some 10 minutes later.

The Israeli defense forces spokesperson said on the IDF's official Twitter account that the chief of staff has ordered the navy to board the vessels after all attempts to contact them failed.

The 27 activists from countries including the United States, Canada, and Ireland set sail from Turkey on Wednesday. They say their goal is to deliver medical aid directly to Palestinians in Gaza, in defiance of Israel's blockade.

Israeli military officials have said they are prepared to intercept the two boats.

Israel imposed a naval blockade on the Hamas-ruled territory in 2007 in what Israeli officials say is a bid to keep weapons from reaching militants in Gaza.

On Thursday, the U.S. State Department renewed a call for Americans to avoid participating in the flotilla, saying they could face legal consequences. At least two Americans are on board.

Last year, nine activists were killed after Israeli commandos stormed a Turkish-led aid flotilla headed for Gaza. The confrontation caused a deterioration in relations between Turkey and Israel.

In July, pro-Palestinian activists launched an unsuccessful attempt to reach the Palestinian territory.