BAGHDAD — Iranian-backed militiamen withdrew from the U.S. Embassy compound in Baghdad on Wednesday after two days of clashes with American security forces, but U.S.-Iran tensions remain high and could spill over into further violence.

The withdrawal followed calls from the government and senior militia leaders. It ended a two-day crisis marked by the breach of the largest and one of the most heavily fortified U.S. diplomatic missions in the world.

The attack and its volatile aftermath prompted the Pentagon to send hundreds of additional troops to the Middle East and U.S. Secretary of State Mike Pompeo to delay a European and Central Asian trip.

In an orchestrated assault, hundreds of militiamen and their supporters broke into the embassy compound, destroying a reception area, smashing windows and spraying graffiti on walls to protest U.S. airstrikes against an Iran-backed militia over the weekend that killed 25 fighters.

The U.S. blamed the militia for a rocket attack on an Iraqi military base in the northern city of Kirkuk last week that killed a U.S. contractor.

The protesters set up a tent camp overnight and on Wednesday set fire to the reception area and hurled stones at U.S. Marines guarding the compound, who responded with tear gas. There were no injuries on either side and no American staff were evacuated from the compound.

The Popular Mobilization Forces, an umbrella group of state-allied militias — many backed by Iran — called on its supporters to withdraw in response to an appeal by the Iraqi government, saying “your message has been received.”

By late afternoon the tents had been taken down and the protesters relocated to the opposite side of the Tigris River, outside the so-called Green Zone housing government offices and foreign embassies. U.S. Apache helicopters circled overhead.

“After achieving the intended aim, we pulled out from this place triumphantly,“ said Fadhil al-Gezzi, a militia supporter. “We rubbed America’s nose in the dirt.” Trump has vowed to exact a “big price” for an attack he blamed squarely on Iran.

Kataeb Hezbollah, the Iran-backed militia targeted by the U.S. airstrikes, initially refused to leave but later bowed to demands to disperse. The militia is separate from the Hezbollah militant group in Lebanon, though both are backed by Iran.

“We don’t care about these planes that are flying over the heads of the picketers. Neither do we care about the news that America will bring Marines,” said Mohammed Mohy, a spokesman for Kataeb Hezbollah. “On the contrary, this shows a psychological defeat and a big mental breakdown that the American administration is suffering from,” he said, before withdrawing from the area.

The violence came as Iran and its allies across the region have faced unprecedented mass protests in recent months and heavy U.S. sanctions have cratered Iran’s economy.

Iraq has been gripped by anti-government protests since October fueled by anger at widespread corruption and economic mismanagement, as well as Iran’s heavy influence over the country’s affairs. Those protesters were not involved in the embassy attack.

The Pentagon sent an infantry battalion of about 750 soldiers to the Middle East. A U.S. official familiar with the decision said they would go to Kuwait. Pompeo postponed a trip that was scheduled to start in Ukraine late Thursday so that he can monitor developments in Iraq and “ensure the safety and security of Americans in the Middle East,” said State Department spokeswoman Morgan Ortagus.

Iran denied involvement in the attack on the embassy. Supreme Leader Ayatollah Ali Khamenei was quoted by media as saying that “if the Islamic Republic makes a decision to confront any country, it will do it directly.”

Iran later summoned the Swiss charge d’affaires, who represents American interests in Tehran, to protest what it said was warmongering by U.S. officials.

Public consular operations at the embassy were suspended and future appointments canceled, it said in a statement.

Tensions have steadily risen since Trump withdrew the U.S. from Iran’s 2015 nuclear deal with world powers and embarked on a campaign of maximum pressure through economic sanctions. Iran has responded by abandoning some of its commitments under the deal.

U.S. officials have blamed Iran for the sabotage of oil tankers in the Persian Gulf and a drone attack on Saudi oil facilities in September that caused a spike in world oil prices. But the Trump administration has not responded with direct military action, apparently fearing a wider conflict.

The U.S. has sent more than 14,000 additional troops to the Gulf region since May in response to concerns about Iranian aggression. At the time of the attack, the U.S. had about 5,200 troops in Iraq.