The leader of Haiti’s transitional presidential council tried to allay surging alarm among Haitians over rampant gang violence by acknowledging Thursday that the country has “become hell for everyone” and promising new measures to stop the bloodshed.

Fritz Alphonse Jean spoke a day after gunfire erupted in the capital, Port-au-Prince, as thousands of protesters demanding an end to gang violence clashed with police outside the offices of the council and the prime minister. It was the…