Supporters of ousted President Mohammed Morsi throw stones towards opponents of Morsi during clashes on a bridge in downtown Cairo, Egypt, July 15, 2013. (Credit: Hussein Malla)

Egypt's interim cabinet was sworn in today after at least seven people were killed and 261 injured in clashes between supporters of ousted President Mohammed Morsi and police early this morning.

According to state-run media, at least 400 people were arrested overnight, but the Muslim Brotherhood put the number much higher.

Brotherhood spokesman Gehad El-Haddad took to Twitter late today to report "7 deaths by live rounds, 647 wounded, 3 critically wounded w/ live rounds, 500 arrested."

The violence kicked off Monday night when police fired tear gas at Morsi supporters blocking traffic on the 6th of October bridge, and major roadways near Cairo's central Ramses Square. Egyptian prosecutors have already called for an investigation into the violence, which promises to deepen the tension between the Islamists and the military.

Today on state television, Egypt's interim President Adly Mansour swore in 34 ministers, mostly liberals and technocrats, to replace Morsi's dissolved Islamist government. Not one Islamist was named to the interim cabinet. Mansour said he offered positions to the Brotherhood and the ultra-conservative Nour Party but both refused to take part in the military's caretaker government.

The Brotherhood's spokesman, Haddad, told Reuters: "It's an illegitimate government, an illegitimate prime minister, an illegitimate cabinet. We don't recognize anyone in it."

The Brotherhood vowed to continue protesting peacefully, calling for nationwide marches on Friday. But Egypt's military spokesman, Col. Ahmed Mohamed Ali told the BBC that last night's protests were anything but peaceful.

"That was not peaceful protesting. We had armed protesters. The role of the military is to defend the military units and facilities… the Egyptian forces have never been created to kill Egyptians or to be killed by Egyptians," Ali said.

In a further sign of the military's grip on power, Army chief Gen. Abdul-Fattah el-Sissi was sworn in again as minister of defense, the post he currently holds, and as first deputy to interim Prime Minister Hazem El-Beblawi.

Earlier this week, Sissi and Beblawi both met with Deputy Secretary of State William J. Burns during his two-day visit to Cairo, who urged them to include the Brotherhood in the political process.

"We've called on the military to avoid any politically motivated arrests and we have also called upon those who differ with the government to adhere to their absolute obligation to participate peacefully," Burns said today. The Brotherhood reportedly refused to meet with Burns.

Secretary of State John Kerry also landed in the region today for the seventh time in as many months to meet with leaders from the Arab League in Amman, Jordan. The group, which largely supports the Egyptian military, is expected to discuss Egypt's transition on Wednesday.