Continuing a practice that has lasted over three decades, India and Pakistan on Thursday exchanged lists of their nuclear facilities under a bilateral agreement that bars attacks on each other’s atomic installations. The exchange occurred despite strained relations between the two nations following four days of military clashes last May.

According to the Ministry of External Affairs (MEA), the list swap was conducted simultaneously through diplomatic channels in New Delhi and Islamabad, in line with the agreement prohibiting attacks on nuclear installations. “India and Pakistan today exchanged, via diplomatic channels, the list of nuclear installations and facilities covered under the agreement on the prohibition of attack against nuclear installations and facilities,” the MEA stated.

The agreement, signed on December 31, 1988, and enforced from January 27, 1991, requires both countries to notify each other of their nuclear facilities on January 1 each year. “This marks the 35th consecutive annual exchange, with the first having taken place on January 1, 1992,” the MEA added.