An important northern Syrian city held by the Islamic State, the group’s last major outpost in the region, was practically surrounded Monday by pro-government and insurgent forces squeezing it from different directions, according to rebels and the state-run Syrian news media.

The city — Al Bab, in Aleppo Province, 15 miles south of the Turkish border — has been hemmed in for months by insurgent fighters and Turkish troops, who have together blocked approaches from the east, north and west, according to rebels working with Turkey, as well as local activists and the Syrian Observatory for Human Rights, a monitoring group.

But now the Syrian Army, aided by Hezbollah militia fighters and artillery units supplied by Russia, has cut off the approach to Al Bab from the south, the Syrian Observatory said Monday. The state-run news media corroborated its account, saying the pro-government forces had captured a hill overlooking a southeastern route out of Al Bab, the last road not already blocked by the Turkish troops and rebels. […]