The Houthis struck an airbase in Khamis Mushait and oil infrastructure in nearby Saudi cities on Tuesday, injuring 73 people in one of the biggest attacks on the kingdom since the US-Israeli war with Iran began in February.
Houthi military spokesman Yahya Saree said on Wednesday that Saudi warplanes had carried out 54 airstrikes across several Yemeni provinces over the previous 12 hours. He warned that the strikes would "not go unanswered and unpunished".
The escalation has opened another front threatening global energy supplies, as Iran and the United States engage in their biggest declared wave of attacks on shipping in the Gulf since the war began.
Pakistan's warning carries particular weight because of its defence agreement with Saudi Arabia and Turkey.
Defence Minister Khawaja Asif said attacks spilling into Saudi territory could activate a joint security arrangement involving Riyadh, Ankara and Islamabad.
"An aggression on one country will be considered an aggression on all three countries," Asif said on Pakistani television.
"There is no ambiguity or doubt... Unprovoked aggression or spillover... into Saudi Arabia will definitely make this agreement operational."
Pakistan's defence and foreign ministries, as well as its military, did not respond to a Reuters request for comment.
Fears of proxy war becoming wider regional crisis
Pakistan's intervention highlights the seriousness of the Houthi attacks after years of balancing its relations with both Saudi Arabia and Iran.
A senior regional diplomat said Islamabad had conveyed a message to Tehran within the previous 24 hours, urging Iran to use its influence to halt Houthi attacks on Saudi Arabia.
A senior Iranian official confirmed that Pakistan had delivered the message on Tuesday. Tehran's response was that "Iran does not control the Houthis".
However, two Iranian sources said Tehran had instructed the Houthis last week to attack Saudi Arabia and promised additional funding and weapons. They also said several Islamic Revolutionary Guard Corps commanders had travelled to Yemen to help coordinate the attacks.
The regional diplomat said Islamabad was seeking to contain the situation before the escalation reached a point where Riyadh could ask Pakistan to play a more direct role in Saudi Arabia's defence.
"Pakistan has an agreement with Saudi Arabia, but I am hopeful the situation will not reach the point where Pakistan has to practically step in," the diplomat said. "It will pursue a diplomatic solution for now."
Pakistan weighs military support for Saudi Arabia
The Pakistani source said Saudi officials had met senior Pakistani and Turkish military representatives in Riyadh to coordinate their response.
The three countries agreed that their troops would not enter Yemen and that any response would be launched from Saudi territory, the source said.
A second Pakistani source said no decision had been made to join retaliatory strikes. The source stressed that Pakistan's military pact with Riyadh was defensive and limited to protecting Saudi territory.
Pakistani forces could provide military, technical, ground or air support inside Saudi Arabia, but would not participate in combat operations on foreign soil, the source said.
The regional diplomat said Iran and the Houthis could ultimately strengthen the security cooperation they are seeking to weaken.
By targeting Gulf security to pressure Washington over its blockade of Iranian ports, Tehran risks pushing Saudi Arabia, Pakistan, Turkey and other US-aligned countries towards closer coordination.
US blockade of Iran expected to continue
Regional officials see little indication that Washington is prepared to ease its pressure on Iran.
President Donald Trump appears committed to maintaining the US blockade until Tehran reaches an agreement with Washington, the diplomat said. Qatar, meanwhile, is quietly exploring proposals aimed at bringing the two sides back to negotiations.
Another regional source said Saudi Arabia's military response would remain focused on the Houthis rather than Iran itself.
Saudi officials also do not believe Houthi attacks will achieve Tehran's broader objective of forcing Washington to end the blockade, the source said.
Riyadh is not expected to pressure Washington to lift the blockade, with Trump believing sustained economic pressure is the most effective way to bring Iran back to negotiations.
"The question is how much pain Iran can absorb, and for how long," the source said. "Trump does not want a military solution. He wants to squeeze them through the blockade."
