BAGHDAD (AP) — Two rockets were fired into the capital’s fortified Green Zone Monday evening, landing around one kilometer (a half-mile) from the U.S. Embassy amid soaring tensions between the U.S. and Iran.

Residents heard the explosions followed by alert sirens that sounded briefly across the Tigris River. It was the second such attack since May, when a rocket was fired into the Green Zone, landing near the sprawling U.S. Embassy compound. Such attacks have been blamed on Iranian-backed militias in Baghdad, some of whom want U.S. troops stationed in Iraq to leave.

Monday’s attack comes amid heightened tensions in the region following an attack on Saudi oil installations that the U.S. and Britain have blamed on Iran.

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There also has been a series of airstrikes on bases belonging to Iran-backed militias in Iraq that the militias have blamed on Israel and its U.S. ally by extension. Israel, which frequently targets Iranian interests in neighboring Syria, has not confirmed its involvement in the airstrikes inside Iraq.

Officials said there was no word of casualties from Monday’s attack, which coincided with a sound bomb targeting a club in central Baghdad that caused damage to cars parked outside.

The officials spoke on condition of anonymity in line with regulations.

As tensions escalate between the U.S. and Iran, there have been concerns that Baghdad could once again get caught in the middle. Baghdad’s fragile government is allied with both sides and has struggled to remain neutral in the conflict.

Earlier this year, the U.S. ordered nonessential staff out of its diplomatic posts in Iraq after an alleged, unexplained threat from Iran.