At General Suleimani’s funeral in Tehran on Monday, military commanders promised vengeance. Iran’s supreme leader, Ayatollah Ali Khamenei, told advisers that any retaliation against the United States should be direct, proportional and carried out openly by Iran.

That is a startling departure for the Iranian leadership, which has typically cloaked its attacks behind the actions of proxies it has cultivated around the region. But in the fury generated by the killing of General Suleimani, a close ally and personal friend of the supreme leader, the ayatollah was apparently willing to cast aside those traditional cautions.

Warnings to United State citizens were sent by American diplomats not only in the Middle East but also in Asia.

The American Embassy in Beijing, citing “heightened tension in the Middle East,” advised American citizens on Tuesday to keep a low profile, be aware of their surroundings, stay alert in tourist locations, review personal security plans and ensure that their travel documents were updated and accessible. American citizens in South Korea said they had received similar warnings.

American diplomats in the Middle East began sending advisories earlier in the week.

American embassies across the region have been on heightened alert since Dec. 31, when militants, backed by the Iranian government, stormed the embassy in Baghdad. President Trump said the assault was organized by General Suleimani.

Last week, embassies in Baghdad and in Beirut, Lebanon, issued security alerts. Some airlines have halted flights to the Iraqi capital, including EgyptAir, which on Tuesday announced that its flights in and out of the city would stop from Wednesday through Friday.

Iran’s Parliament labeled the Pentagon’s leadership ‘terrorists.’