Iran activated its air defense system overnight and says that Israel has not conducted a missile attack on the country, amidst widespread reports that drones were seen over Isfahan, Iran and that Israel has launched an attack.

According to reports at the Wall Street Journal, Iran activated the defense system and cancelled flights as media reported an explosion in the country.

The information has raised alarm amongst the international community, which has braced itself for the possibility of an attack on Iran by Israel. The fear is that a counterattack by Israel would elevate the conflict in the Middle East and draw larger global powers into the fray.

An Iranian official told Reuters on Friday morning that the explosions heard in Isfahan and reported on Iranian media were caused by the activation of the air defense system, and not by a missile attack by Israel.

However, widespread Iranian media reports say that drones were reported over an army base in the centrally located city of Isfahan.

Sources have told Reuters that Israel indeed attacked Iran with drones, but that they were destroyed by Iran’s military forces. Additionally, Reuters reports that the U.S. was not involved, but that it was informed of Israel’s intentions in advance of the attack.