CAIRO — Egyptian troops opened fire today on mostly Islamist protesters marching on a Republican Guard headquarters to demand the restoration of ousted President Mohammed Morsi, killing at least one.

The shooting came as tens of thousands of his supporters chanting “down with military rule” rallied around the country.

The shooting came when hundreds of Morsi supporters marched on the Guard building, where Morsi was staying at the time of his ouster before being taken into military custody in an unknown location. The crowd approached a barbed wire barrier where troops were standing guard around the building.

When one supporter hung a sign of Morsi on the barrier, the troops tore it down and told the crowd to stay back. A protester hung a second sign and the soldiers opened fire on the crowd. Several protesters were wounded, many with the pockmark wounds typical of birdshot.

At least one had a gaping, bleeding exit wound in the back of his head. Fellow protesters carried the body into a building and covered his head with a blanket, declaring him dead, according to AP Television News footage.

Health Ministry official Khaled el-Khatib confirmed that one protester was killed today and a number wounded, but he did not know the exact number.

Protesters pelted the line of troops with stones, and the soldiers responded with volleys of tear gas, but the clashes appeared for the moment to ease with mid-afternoon prayers.