ISLAMABAD: The Foreign Office in Islamabad on Saturday advised Pakistanis to avoid unnecessary travel to Iran, while those who have already been in the Islamic republic were asked to exercise caution, following an Israeli attack on Iran.

Israeli Defense Minister Israel Katz confirmed his country had launched the attack and declared a state of emergency as thick smoke rose from an explosion in downtown Tehran, Iran’s capital, AP reported.

It wasn’t immediately clear what the target of the Israeli attack was. But it comes as the United States has assembled a vast fleet of fighter jets and warships in the region to try to pressure Iran into a deal over its nuclear program.

Sounds of three explosions were heard in central Tehran, state media reported, while FARS news agency reported that several missiles have struck University Street and the Jomhouri area.

“Pakistani nationals are advised to avoid all non-mandatory travel to the Islamic Republic of Iran,” the Pakistani foreign office said in a statement.

“Pakistani nationals currently residing in Iran must exercise caution, remain vigilant, minimize non-essential travel, and stay in regular contact with the Pakistani missions.”

Sirens sounded across Israel at the same time. The Israeli military said that it had issued a “proactive alert to prepare the public for the possibility of missiles being launched toward the state of Israel.”

The Israeli Broadcasting Authority reported it was a joint Israeli-American attack on Iran. The US military declined to immediately comment on the attack.

Foreign airlines have suspended flights to Israel and were returning to their original destinations, media reports indicated.

— With input from AP.