Egypt's military on Monday said mass protests calling for the resignation of Islamist President Mohammed Morsi were an "unprecedented" expression of the will of the people and gave the government 48 hours to meet the opposition's demands, NBC News reports.

In a statement read on state television just hours after the headquarters of Morsi's Muslim Brotherhood movement were ransacked, General Abdel Fattah al-Sisi said if this did not happen the army would intervene, NBC News also reports.

"If the demands of the people are not realized within the defined period, it will be incumbent upon (the armed forces)... to announce a road map for the future," the statement read.

Unrest has grown in Egypt between supporters of Mohammed Morsi, joined by the Muslim Brotherhood, and those who oppose the incumbent Islamist government administration.

Those opposing Morsi and the Muslim Brotherhood accuse their administration of implementing ultra-religious legislation and centralizing political power in Egypt.

"We're all concerned about what's happening in Egypt," President Barack Obama said in a statement, urging all sides to retain from violence, according to NBC News.

"There is more work to be done to create the conditions in which everybody feels that their voices are heard and that the government is responsive and truly representative." 

Gehad El-Haddad, the Brotherhood's spokesman, used his Twitter feed to urge Egyptians to "go to the streets all across the country in refusal of any attempted coup," a reference to the military's ultimatum, the Kansas City Star reports.

No further comments have been made by the Egyptian military.