China on Wednesday urged Pakistan and Iran to show "restraint", after Islamabad said Tehran had carried out an air strike on its territory that killed two children.
"We call on both sides to exercise restraint, avoid actions that would lead to an escalation of tension and work together to maintain peace and stability," foreign ministry spokeswoman Mao Ning told a regular briefing.
"We consider both Iran and Pakistan as close neighbours and major Islamic countries," she said.
Tuesday's strike in Balochistan province has imperilled diplomatic relations between the two neighbours – Iran and nuclear-armed Pakistan have long regarded each other with suspicion over militant attacks. However, both sides appeared wary of provoking the other.
In state media reports, which were later withdrawn without explanation, Iran said its paramilitary Revolutionary Guard targeted bases for the militant group Jaish al-Adl, or the “Army of Justice". The group, which seeks an independent Balochistan and has spread across Afghanistan, Iran and Pakistan, acknowledged the assault in a statement shared online.
Six bomb-carrying drones and rockets struck homes that the militants claim housed children and wives of their fighters. Jaish al-Adl said the attack killed two children and wounded two women and a teenage girl.
Videos purportedly from the site, shared by the Baloch activist group HalVash, showed a burning building and two charred, small corpses.
Pakistan’s Foreign Ministry said it issued a strong protest late Tuesday with Iran's foreign ministry, and summoned an Iranian diplomat in Islamabad “to convey our strongest condemnation of this blatant violation of Pakistan’s sovereignty".
"The responsibility for the consequences will lie squarely with Iran,” it said.
However, there were signs Pakistan was trying to contain any anger over the strike. The country's typically outspoken and nationalistic media covered the attack Wednesday with unusual restraint.
Jaish al-Adl was founded in 2012, and Iranian officials believe it largely operates in Pakistan. The group has claimed bombings and kidnapped members of Iran's border police in the past.
Iran has fought in border areas against militants, but a missile-and-drone attack on Pakistan is unprecedented.
It remains unclear why Iran launched the attack now, particularly as its foreign minister had met Pakistan's caretaker prime minister the same day at the World Economic Forum in Davos, Switzerland.