A British Navy ship on Sunday evacuated about 100 British citizens from the Libyan capital, Tripoli, as 25 Libyans were reported killed in the fighting between rival militias that has torn apart the city and destroyed its airport.

The scenes of anxious foreigners fleeing by boat recalled the mayhem at the start of the Libyan uprising under Col. Muammar el-Qaddafi in 2011, though Tripoli residents say the violence has now become more severe than at any time during the revolt or since. What began three weeks ago as a relatively isolated battle for the airport has spread to round-the-clock skirmishes in pockets throughout the city. More than 200 are believed to have died in the fighting.

The battle in the capital is part of a sharp escalation in a national struggle between the allies and opponents of the political Islamist movement. The contest is already dividing the newly elected legislature, set to convene Monday for its first formal session. But the tensions between the two sides had been building for more than a year as the Islamists and their militia allies flexed their muscles, both in Parliament and in the streets. […]