U.S. President Donald Trump warned in a tweet on Sunday that the U.S. is targeting 52 sites in Iran and will hit them "very fast and very hard" if the Islamic Republic of Iran attacks American personnel or assets.

Mourners attend the funeral of the Iranian Major General Qassem Soleimani and the Iraqi militia commander Abu Mahdi al-Muhandis in Baghdad, Iraq, January 4, 2020. (Photo: CGTN)

Trump's latest response came after the assassination of Qassem Soleimani in a U.S. air strike on Baghdad airport on Friday morning.

Tensions have been rising with Tehran vowing to avenge the death of Soleimani and the U.S. is deploying some 3,500 additional troops to the Middle East region to boost security.

Iran's Supreme Leader Ayatollah Ali Khamenei on Friday appointed Esmail Ghaani as the new commander of the Quds Force of Islamic Revolution Guards Corps (IRGC).