A powerful blast from explosives planted in a tunnel under the Old City of Aleppo, in northern Syria, killed or wounded 20 government troops Tuesday, activists said.

Jabha Shamiyeh, a new rebel coalition in Aleppo, was behind the blast, said the Syrian Observatory for Human Rights, which was not immediately able to give a breakdown of the dead and wounded.

The explosion “killed and wounded at least 20 troops and loyalists,” said the Observatory, which relies on a broad network of sources for its reporting. […]