“They are coming from the east of the city, and the west,” he said by telephone, with the sound of heavy gunfire in the background. “Today, they are coming powerfully,” he said, excusing himself as the fight drew near.

Around 3:45 p.m., a huge explosion near the Turkish border at first seemed like an airstrike, with no sound of aircraft overhead. “I can’t tell what it is,” said Ismat Sheikh Hasan, the defense minister for the Kurdish People’s Protection Committees, known as the Y.P.G. “They have been trying to advance since the morning,” he said, adding that the militants appeared to have been resupplied with weapons.

Anwar Muslim, a lawyer and the head of the Kobani district, who was in the area at the time of the explosion, said it was either a “suicide attack or a car bomb.”

“They are using all ugly ways to try to advance,” he said. “We had less airstrikes today and we have no idea why.”

The fighting in Kobani unfolded on Friday, as it has for weeks, in front of an audience, including residents of nearby towns and villages, some of whom have relatives living or fighting in the city. They sat watching on the edge of corn and cotton fields. The audience also included dozens of journalists, as well as Turkish troops, sitting in armored vehicles, whose inaction during the fighting has fueled a rising anger among Kurds on both sides of the border.

The city, seen through binoculars on Friday, bore the scars of heavy weapons. A large glass building in the center appeared badly damaged, as did as a white building to the east, on top of which flew the black flag of the Islamic State.