PARIS—France froze assets of Iran’s intelligence agency and two agents in retaliation for an alleged Iranian terror plot on French soil, seeking to punish Tehran for planning terror activities in Europe even as the French government tries to salvage the Iran nuclear deal.

The freeze will apply for at least six months to two officials—Assadollah Asadi and Saeid Hashemi Moghadam—whom European authorities allege were involved in the foiled attack, and the internal security directorate of Iran’s intelligence ministry.

The...