Iran claimed it struck bases belonging to Jaish al-Adl, a Sunni militant group in Pakistan, in a cross-border attack Tuesday.
It comes after Iran launched similar attacks on Syria and Iraq over the past several days.
What do we know about the reported Iranian attacks on Pakistan?
Iranian state media reported that drones and missiles were used in the operation.
Pakistan's Foreign Ministry confirmed the attack, condemning it as an "unprovoked violation" of its airspace. It said that two children were killed in the incident and three people injured.
"This violation of Pakistan's sovereignty is completely unacceptable and could have serious consequences," a Foreign Ministry statement read.
Why is there tension between Pakistan and Iran?
Beyond fears that the incident could further inflame the already tense situation growing around the conflict in Gaza, it rings ominous for relations between nuclear-armed Pakistan and nuclear-ambitious Iran.
The two have long eyed one another warily while at the same time seeking to maintain diplomatic relations.
Though Iran has engaged Jaish al-Adl militants in border skirmishes in the past, the execution of cross-border missile attacks had never taken place.