Haifa, Israel ? Israeli warships attacked at least one of six ships carrying pro-Palestinian activists and aid for the blockaded Gaza Strip, killing at least two and wounding an unknown number of people on board, an Arabic satellite news channel and a Turkish TV network reported early today.

The Israeli military spokesman’s office denied that its forces attacked the boats but said they would enforce the decision to keep them away from Gaza.

However, other security officials, speaking on condition of anonymity because they were not authorized to report on the military operation, confirmed that activists were wounded, but did not give numbers.

They said the troops faced resistance and that soldiers were under orders only to use fire if their lives were in danger.

The al-Jazeera satellite channel reported by telephone from the Turkish ship leading the flotilla that Israeli navy forces fired at the ship and boarded it, wounding the captain. The Turkish NTV network also reported an Israeli takeover with gunfire, and that at least two people were killed.

The al-Jazeera broadcast ended with a voice shouting in Hebrew, “Everybody shut up!”

A Turkish website showed video of pandemonium on board one of the ships, with activists in orange life jackets running around as some tried to help an activist apparently unconscious on the deck. The site also showed video of an Israeli helicopter flying overhead and Israeli warships nearby.

The reports came just after daybreak, with the flotilla still well away from the Gaza shore. Israel had declared it would not allow the ships to reach Gaza.

Al-Jazeera footage showed soldiers descending from helicopters on ropes onto a ship and two men, apparently wounded, being carried away.

A violent takeover would deal yet another blow to Israel’s international standing, already tarnished by war crimes accusations in Gaza and its three-year-old blockade of the impoverished Palestinian territory.

Greek activists said people on board one of the ships in the flotilla told them that Israeli forces boarded two other boats — one Greek, another Turkish — from helicopters and inflatable speedboats and took them over.

They said the attack took place in international waters 80 miles from the Gaza coast and that the boat had refused to obey the Israeli navy’s orders to halt.

Shortly after, activists on board the ship told them that Israeli commandos had boarded the Greek boat and that the last words they heard before the connection was cut were, “They’re boarding the ship using hooks, we’re under arrest.”

The head of the Gaza Hamas government, Ismail Haniyeh, condemned the “brutal” Israeli attack.

“We call on the Secretary-General of the U.N., Ban Ki-moon, to shoulder his responsibilities to protect the safety of the solidarity groups who were on board these ships and to secure their way to Gaza,” Haniyeh told The Associated Press.

Turkish television stations said police blocked dozens of stone-throwing protesters who tried to storm the Israeli consulate in Istanbul. The CNN-Turk and NTV televisions showed dozens of angry protesters scuffling with Turkish police and shouting, “Damn Israel.”

On Sunday, Huwaida Arraf, one of the organizers, said the six-ship flotilla began the journey from international waters off the coast of Cyprus on Sunday afternoon after two days of delays. She said they expected to reach Gaza, about 250 miles away, this afternoon, and that two more ships would follow in “a second wave.”

The flotilla was “fully prepared for the different scenarios” that might arise, and organizers were hopeful that Israeli authorities would “do what’s right” and not stop the convoy, she said.

“We fully intend to go to Gaza regardless of any intimidation or threats of violence against us,” she said. “They are going to have to forcefully stop us.”

After nightfall Sunday, three Israeli navy missile boats left their base in Haifa, steaming out to sea to confront the activists’ ships.

Two hours later, Israel Radio broadcast a recording of one of the missile boats warning the flotilla not to approach Gaza.

“If you ignore this order and enter the blockaded area, the Israeli navy will be forced to take all the necessary measures in order to enforce this blockade,” the radio message continued.