Demonstrators holding flags protest against against an attack by Israeli forces on the international Gaza aid flotilla that has killed 20 people, including Turkish activists,in Istanbul, Turkey, Monday, May 31, 2010. [Xinhua/AFP]

About 10,000 Turkish protestors gathered in Istanbul on Monday to demonstrate against an attack by Israeli forces on the international Gaza aid flotilla that has killed 20 people, including Turkish activists.

Holding Palestinian and Turkish flags, the protestors gathered in Taksim square in central Istanbul, chanting slogans against killing activists who were on board boats carrying humanitarian aid to Gaza.

Some supporters even shouted slogans, calling on Turkish troops to intervene in Gaza against the Israeli army.

They first gathered before the Israeli consulate in the city to protest the Israeli threats against the flotilla that was trying to break a blockade on the coastal enclave.

More protesters soon joined the gathering before the mission located in Istanbul's central Levent district early Monday soon after midnight local time.

The predominantly-religious crowd of nearly 2,000 demonstrators spilled into the streets, disturbing traffic at one of Istanbul's busiest streets, and shouted anti-Israel slogans and held up Palestinian flags and Islamic banners.

Police removed the protesters from the foyer of building and back behind the barriers, when news of Israel's violent intervention against the six-ship relief flotilla reached the protesters.

Vendors in the streets set up stands selling Palestinian and Islamic banners and headbands condemning Israel.

This is just a spark that "will extend from Turkey and spread to the world," protester Hakan Erden, a 40-year-old advertiser, told Xinhua.

Israel made a huge mistake, according to protester Menderes Arican, a 45-year-old shopkeeper. "It shouldn't have done this; this is something you don't do even if you are told to."

Arican said the attack was the "beginning of the end for Israel, " adding losing a friendly country like Turkey and being alone in the world was a mistake.

Protestor Ibrahim Dogan, 49, told Xinhua that Israel will now be isolated in the worldwide public opinion, saying that "Israel's supporters in Turkey and in the world will not be able now to defend it."

Resat Baser, an official with the Human Rights and Freedoms Humanitarian Aid Foundation, said they had received information that the ships were taken to Israel's Haifa Port but could not confirm the information.

Turkish Foreign Ministry on Monday strongly condemned the attack, warning the move could damage the two countries' relations.

The ministry has summoned the Israeli ambassador for an urgent explanation of the issue, according to a statement by the ministry.

Israel has been imposing a tight blockade on the Gaza Strip since the Islamic Hamas movement seized control of the enclave by force in June 2007. However, Israel said that in spite of the blockade, it allowed food, fuels and humanitarian aid into the enclave over the past three years.

The flotilla consisted of six ships carrying about 10,000 tons of aid and had set sail from a port in Cyprus on Sunday. It was scheduled to reach Gaza by Monday morning.

The flotilla, originally made up of nine ships from Turkey, Britain, Ireland, Greece, Kuwait and Algeria, were carrying cement, water purification systems and wheelchairs. One of the ships had not arrived and two others had been damaged.