Thousands of Muslim Brotherhood supporters demonstrated in a Cairo square Friday, waving pictures of ousted president Mohammed Morsi, as Egypt’s Prime Minister chose a leftist politician as deputy prime minister.

Demonstrators chanted anti-military slogans, calling the army chief a traitor. He led the military's removal of Morsi from office last week.

The unseating of Morsi followed demonstrations by millions of Egyptians against his rule. It was a bitter blow to the Brotherhood, which won a string of ballots, including Morsi's election as president.

One speaker at the Friday demonstration pledged to stay on the streets until Morsi is reinstated.

"We are ready to stay for a month, two months, a year or even two years," ultraconservative Islamist Salafi cleric Safwat Hegazi told protesters.

This week more than 50 pro-Morsi protesters were killed in a clash with the military.

Meanwhile, Reuters reported that the country’s interim authorities nominated attorney Ziad Bahaa El-Din, who is a member of the leftist Egyptian Social Democratic Party, as deputy prime minister.

``I have chosen Dr. Bahaa El-Din as deputy prime minister and sent the nomination to the president,'' Prime Minister Hazem el-Beblawi said Friday, according to Reuters.

Beblawi also said he was holding talks with other candidates for his new cabinet that he expects to be formed within a few days. Economist Beblawi was named prime minister to lead a military-backed government following the military's overthrow of Morsi.

Reuters and the Associated Press contributed to this report.