CAIRO — Egyptian police in riot gear swept in with armored vehicles and bulldozers today to clear two sprawling encampments of supporters of the country’s ousted Islamist president in Cairo, showering protesters with tear gas as the sound of gunfire rang out. At least 15 people were killed.

Smoke clogged the sky and fires smoldered on the streets, which were lined with charred poles and tarps after several tents were burned. The smaller camp was cleared relatively quickly, but clashes were ongoing at the main site near a mosque that has served as the epicenter of the pro-Morsi campaign.

The assault came after days of warnings by the military-backed interim administration that replaced President Mohammed Morsi after he was ousted in a July 3 coup. The two sit-in camps at two major intersections on opposite sides of the Egyptian capital began in late June to show support for Morsi. After the coup, protesters there have demanded his reinstatement.

Clashes also broke out elsewhere in Cairo and other provinces across the country, with police stations, government buildings and churches attacked or set ablaze.

The Egyptian Central Bank instructed commercial banks to close branches in areas affected by the chaos, a sign of alarm that the violence could spiral out of control. The Ministry of Antiquities also ordered the site of the Giza Pyramids closed to visitors along with the Egyptian museum in the heart of the Egyptian capital. The closures were a precaution effective only for today, it said.

The turmoil was the latest chapter a bitter standoff between Morsi’s supporters led by the Muslim Brotherhood and the leadership that has assumed the helm of the Arab world’s most populous country.