A group of Palestinian fishing boats sailing off the coast of Gaza to challenge an Israeli naval blockade of the coastal enclave drew warning shots from the Israeli navy on Saturday, protesters said.
About 20 fishing boats set off from Gaza City towards the sea border with Israel. The Ministry of Health in Gaza said no casualties were reported.
An Israeli military spokeswoman said the navy warned the boats verbally before firing in the air.
Palestinian witnesses said some of those present had set fire to tires and thrown them to the maritime border before confronting four Israeli warships.
Israel says its naval blockade of Gaza is designed to prevent arms from reaching militant groups, including Hamas, the political party that controls the Palestinian territory. Israel and some western countries claim that Hamas is a terrorist organization.
More than 2 million Palestinians have been forced into the Gaza Strip, which is in dire economic predicament.
Israel and Egypt, relying on security issues, are severely restricting their land transfers with Gaza, which has brought their economy into collapse.
Israel and Hamas, which have fought three wars since 2008, will launch a long-term ceasefire between the United Nations and Egypt. The offer should also address the humanitarian problems in Gaza and improve its economy.
Adham Abu Selmeya, one of the flotilla organizers, said the event should send a message to all parties involved in the ceasefire efforts.
"We want the world to see the reality of the blockade and suffering of the people of Gaza, and we will accept nothing less than lift the blockade once and for all," he said.
Cross-border violence has increased in recent months. Since the beginning of the weekly protests on March 30, the Israeli army has killed 161 Palestinians. An Israeli soldier died.
On Thursday, Egyptian mediation ended a two-day wave of rocket bursts and airstrikes between militant groups in Israel and Gaza.