CAIRO — More than 50 people were killed Monday in clashes in Egypt, but Interim President Adly Mansour moved forward, issuing a swift timetable late Monday for the process of amending the Islamist-backed constitution and setting parliamentary and presidential elections for early 2014.

The killings further entrenched the battle lines between supporters and opponents of ousted President Mohammed Morsi, who was removed by the military July 3.

Morsi’s Muslim Brotherhood called for an uprising, accusing troops of gunning down protesters. The military blamed armed Islamists for provoking its forces.

The battle began during a protest by about 1,000 Islamists outside the Republican Guard headquarters. At least 51 protesters were killed and 435 wounded, most from live ammunition and birdshot, emergency services chief Mohammed Sultan said.

Army Col. Ahmed Mohammed Ali said police and troops came under “heavy gunfire” at around 4 a.m. and attackers on rooftops opened fire with guns and Molotov cocktails. A soldier and two policemen were killed, and 42 in the security forces were wounded, eight critically, he said.