The U.S. Consulate in Sydney was evacuated Monday after a gunman walked into a chocolate shop into the city's central business district and took an unknown number of people hostage.

The consulate also issued an emergency warning to American citizens in the city, calling on them to "maintain a high level of vigilance and take appropriate steps to enhance your personal security." The statement also warned Americans to avoid the area around the cafe on Martin Place until further notice.

State Department spokesman Jen Psaki confirmed that the consulate was evacuated as a security precaution, adding that a small number of essential consular staff continued to work from a secure location. Psaki also said that all of the consulate's Chief-of-Mission personnel had been accounted for.

The consulate is located on Castlereagh Street, just south of the scene of the hostage situation.

Late Sunday, a White House official told Fox News that President Obama had been briefed on the situation by Lisa Monaco, his special assistant for homeland security and counter terrorism.