Media in Iran say the country's elite Islamic Revolutionary Guard Corps has attacked bases of a Sunni militant group in Pakistan, following strikes the IRGC carried out in Iraq and Syria.
The media reported on Tuesday that the IRGC carried out the missile and drone attack on bases of the group in the province of Balochistan in southwestern Pakistan.
The Iranian government says the militant group is hostile to Shia-majority Iran and has repeatedly attacked police buildings in the country.
Pakistan's foreign ministry issued a statement on Wednesday condemning what it called "the unprovoked violation of its airspace by Iran." It says the attack killed two children and injured three girls.
The statement adds, "This violation of Pakistan's sovereignty is completely unacceptable." It says Pakistan has already lodged a strong protest with Iran's foreign ministry.
The attack came on the same day that Iranian state media said the navies of both countries conducted a joint naval exercise.
The IRGC said on Tuesday that it fired missiles late Monday at what it claimed was an Israeli spy headquarters in northern Iraq.
It also said it carried out missile attacks against targets in Syria, calling them retaliation for terrorist attacks staged in Iran by the Islamic State militant group.
Observers said the missile strikes were likely carried out in response to calls from the Iranian people for revenge.
There are concerns that the regional situation may become further unstable.