The U.S. State Department has issued a worldwide alert for American citizens about possible "anti-U.S. actions" following charges against two Iranians accused of conspiring with Tehran to kill the Saudi ambassador to the United States.
The State Department said late Tuesday that the alleged Iranian-backed assassination attempt may indicate the Iranian government could be taking a "more aggressive focus" on terrorist activity.
Earlier Tuesday, the U.S. Justice Department charged Manssor Arbabsiar, a naturalized U.S. citizen with an Iranian passport, and Gholam Shakuri, an Iran-based member of the Iranian Quds force, with conspiring to kill Saudi ambassador Adel al-Jubeir.
U.S. Attorney General Eric Holder said the plot was "conceived, sponsored and directed" from Iran. He promised Washington will hold the Iranian government accountable.
Shortly after the announcement was made, the U.S. Treasury Department announced economic sanctions against Arbabsiar and Shakuri, as well as three officers of Iran's Revolutionary Guard.
President Barack Obama called Ambassador al-Jubeir to express solidarity against the plot, calling it a "flagrant violation" of U.S. and international law. He assured al-Jubeir the U.S. is committed to protecting all diplomats serving in the United States.
Secretary of State Hillary Clinton said Tuesday the U.S. will continue to work with its allies to "further isolate" Iran from the international community.
Iran strongly denies being involved in the assassination attempt. Iran's U.N. ambassador wrote a letter to the United Nations Tuesday expressing "outrage" over the U.S. allegations, calling them politically-motivated "warmongering and propaganda."
Officials say Arbabsiar unknowingly hired an informant of the U.S. Drug Enforcement Administration to carry out the plot, believing the informant had ties to Mexican drug cartels capable of killing the Saudi ambassador. They say Arabsiar confessed to making a $100,000 down payment on the scheme with a price tag of $1.5 million.
Officials arrested Arbabsiar at New York's John F. Kennedy International Airport on September 29, but Shakuri is still at large.