At least 278 people were killed and many more were injured across Egypt after riot police moved to remove supporters of ousted president Mohammed Morsi from public squares. The military-backed leadership, which took over after Morsi's ouster in July, also moved to impose a state of emergency and a curfew amid the violence.
UN Secretary-General Ban Ki-moon condemned "in the strongest terms the violence today in Cairo that occurred when Egyptian security services used force to clear Cairo of sit-ins and demonstrations."
Ban urged all Egyptians to focus on reconciliation, saying he is "well aware that the vast majority of the Egyptian people want their country to go forward peacefully in an Egyptian-led process towards prosperity and democracy."
Foreign Affairs Minister John Baird said in a statement that Canada is "deeply concerned" by reports of deadly violence.
"We urge all parties to refrain from violence and engage in a meaningful political dialogue for the good of all Egyptians."
Baird urged the two sides to sit down and work to reconcile their differences and "work tirelessly to halt this deadly standoff."
The path to reconciliation, however, was unclear on Wednesday as the unrest continued and many Morsi supporters called for continued protests.
The police sweeps in Cairo sparked clashes in the capital city and elsewhere in the country. The condemnation from Western politicians came ahead of an announcement from Egypt's Interior Minister Mohamed Ibrahim. Reuters reported that the interior minister said after the initial police action that sit-ins in "any square in any place in the country" will not be allowed.
Egypt's military-backed government is currently led by interim President Adly Mansour, a veteran of Egypt's constitutional court. Meanwhile, the country's vice-president, Mohamed ElBaradei, resigned as the clashes escalated, saying violence breeds more violence and that he is not prepared to be held responsible for a "single drop of blood."
A statement from the White House extended condolences to the families of those who were killed or injured and said the U.S. "strongly condemns" the use of violence against protesters in Egypt.
"We have repeatedly called on the Egyptian military and security forces to show restraint, and for the government to respect the universal rights of its citizens, just as we have urged protesters to demonstrate peacefully," the statement said.
U.S. Secretary of State John Kerry also expressed concern about the violence, saying it is deplorable and a "serious blow" to reconciliation efforts.
He said the violent events that unfolded are "deplorable and they run counter to Egyptian aspirations for peace, inclusion and genuine democracy."
Kerry said the U.S. opposes the imposition of a state of emergency and urged Egypt's interim leaders to take a step back and calm the situation to avoid further deaths.
He said the promise of Egypt's 2011 revolution "has simply never been fully realized" and said the final outcome of the revolution that ousted longtime leader Hosni Mubarak is not yet decided.
A spokeswoman for the State Department said the U.S. is "constantly evaluating" its relationship with Egypt, which includes aid relationships.
The European Union's top diplomat, Catherine Ashton, who has met with Morsi, said in a statement that "confrontation and violence" is not the way to resolve political issues.
Ashton expressed concern about the loss of life and injuries, and called on security forces to use "utmost restraint" while also urging Egyptians to "avoid further provocations and escalation."
The EU diplomat said Egypt's democratic future depends on "a dialogue among all concerned aimed at overcoming differences in an inclusive process of political reconciliation, with a fully empowered civilian government and functioning democratic institutions."
'The world must stand up,' Muslim Brotherhood says
A statement from the Muslim Brotherhood's media office in London sent to The Associated Press said the world "cannot sit back and watch while innocent men, women and children are being indiscriminately slaughtered. The world must stand up to the military junta's crime before it is too late."
Jordan's Muslim Brotherhood urged its Egyptian peers to continue protests, saying their victory will help the fundamentalist group rise to power elsewhere in the Arab world.
The Brotherhood's political arm, the Islamic Action Front, also warned Egypt's military rulers they have fallen into a "conspiracy" hatched by the U.S. and Israel to weaken Muslims.
Brotherhood members staged a protest outside the Egyptian Embassy in Amman, Jordan, and rebuked Egypt's military rulers as a "tool for corrupt and tyrant military regimes."