CHILMARK, Mass. (CBSDC/AP) — President Barack Obama is calling for an end to the violence in Egypt a day after 525 people were killed in protests across the country.

Speaking from Martha’s Vineyard Thursday, the president strongly condemned security forces going after supporters of ousted Egyptian President Mohammed Morsi.

“America cannot determine the future of Egypt, that’s a task for the Egyptian people,” Obama said. “We don’t take sides.”

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Obama said that, due to the violence, the United States will cancel its bi-annual joint-military exercise with Egypt next month. He added that Egyptians blaming the U.S. for the violence will not help Egypt achieve the democracy it deserves.

“We recognize that change takes time,” Obama stated, while calling on protesters to demonstrate peacefully.

Obama also criticized the interim government imposing a month-long state of emergency and nighttime curfew.

“We oppose the pursuit of martial law,” Obama said.

The violence escalated when riot police began raiding and clearing out camps of Muslim Brotherhood supporters of Morsi. Clashes then spread to Cairo and other cities. The Egyptian Health Ministry says another 3,700 were injured.

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CBS News correspondent Charlie D’Agata described the streets of Cairo as a “war zone.”

D’Agata reports that the Muslim Brotherhood called Wednesday’s deadly day a “massacre” and vowed to topple the “military coup.”

The death toll made Wednesday the deadliest day in Egypt since the 2011 uprising that toppled Hosni Mubarak’s reign.

Morsi was ousted during a military coup July 3 after millions of Egyptians demanded Morsi to step down.

Chaos continued Thursday after hundreds of Muslim Brotherhood supporters stormed a government building in Giza and set fire to it. Morsi supporters called for new protests, but CBS News learned that there were no mass gatherings as of early afternoon.

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