(CNN) -- Syria's major opposition group condemned Bashar al-Assad's regime Wednesday for "horrific massacres" this week and called on the Arab League and the U.N. Security Council to take "necessary measures" to protect civilians.
The Syrian National Council said nearly 250 people have died over a 48-hour period and it urged the Arab League to condemn the killings and work with the United Nations "in taking the necessary measures to protect Syrian civilians."
"The SNC stresses the need to take all necessary actions to stop the bloody campaign that is targeting more cities and towns through the regime's militant expansion," the group said in a news release dated Tuesday but issued Wednesday to CNN via e-mail.
It called for an emergency U.N. Security Council meeting "to discuss the regime's massacres in Zawyiyeh mountain, Idlib, and Homs, in particular; issue international condemnation thereof; declare the cities and towns being brutally attacked 'safe zones' that enjoy international protection; and force the regime's forces to withdraw from said areas."
The group is calling for a declaration "that Zawiyeh mountain, Idlib, and Homs are disaster areas exposed to large-scale genocide and displacement operations by the Syrian regime's militias" and urged the International Red Crescent and other relief organizations "to intervene directly and provide urgent humanitarian assistance."
The violence spiked as Syria agreed to an Arab League peace plan Monday aimed at ending the violence between regime forces and protesters that started in mid-March. The United Nations earlier this month estimated that about 5,000 people have died in the violence.
Other groups also reported a surge in killings this week.
The Local Coordination Committees, an opposition umbrella group, said 84 people were killed across the country Tuesday.
The London-based Syrian Observatory for Human Rights reported a higher death toll of 111, which would make Tuesday among one of the deadliest days since the government crackdown started, activists say.
The Syrian Observatory's Rami Abdul Rahman had said Monday's toll of 100 to 110 was the highest, but Tuesday's total appears to surpass that.
The Syrian government maintains that it is cracking down on armed terrorists who attack security forces and civilians. The activists say the government's brutal crackdown against peaceful protests has led to the deaths.
CNN could not independently verify the allegations because Syria restricts the activity of journalists in the country.
Saad Abedine and Kindah Shair contributed to this report