Iranian state media has accused Saudi Arabia of bombing its embassy in Sanaa, the capital of Yemen.
Saudi Arabia has been carrying out regular air strikes in Sanaa, targeting Houthi rebels, who control the capital.
Some guards were injured, according to state television channel Islamic Republic of Iran Broadcasting (IRIB).
The accusation follows the breakdown of diplomatic relations between the GCC and Iran.
Saudi Arabia, Bahrain, Kuwait and Qatar cut diplomatic relations completely after a mob attacked the Saudi embassy in Tehran on 3 January. The UAE downgraded its relations, while Oman issued a strong condemnation.
The most recent increase in tensions between the GCC and Iran began when Saudi Arabia executed 47 people convicted of terrorism, including prominent Shia cleric Sheikh Nimr al-Nimr.
Saudi Arabia accuses Iran of supporting Houthi rebels, which took over most of Yemen in early 2015, forcing out President Abd Rabbu Mansour al-Hadi.
A coalition led by the kingdom began military operations against the Houthis in March 2015, taking back some of the territory.
Muscat condemned a Saudi air strike in September, which hit the Omani ambassadors residence in Sanaa.
Foreign ministers from GCC states will hold an extraordinary meeting in Riyadh on 9 January to discuss increasing tensions with Iran.