PESHAWAR, Pakistan — Police in Pakistan have arrested a man accused of spreading false information online that fueled anti-immigrant riots in Britain.

Violence erupted across Britain this month after the deaths of three young girls in a July 29 stabbing attack at a Taylor Swift-themed dance class in Southport, England. Rumors quickly spread online that the assailant was a refugee and a radical Islamist, prompting right-wing mobs to attack hotels that house asylum-seekers, as well as mosques…