The UAE, along with several other powerful Arab states, severed diplomatic ties with fellow Gulf state Qatar on Monday over its alleged support for Islamist groups and Iran. Qatar denies the accusations.
US President Donald Trump took sides in the deep rift in the Arab world on Tuesday, praising Middle East countries' actions against Qatar, but later spoke by phone with Saudi King Salman and stressed the need for Gulf unity.
"Strict and firm action will be taken against anyone who shows sympathy or any form of bias towards Qatar, or against anyone who objects to the position of the United Arab Emirates, whether it be through the means of social media, or any type of written, visual or verbal form," Gulf News quoted UAE Attorney-General Hamad Saif al-Shamsi as saying.
On top of a possible jail term, offenders would also be hit with a fine of at least 500,000 dirhams ($AU180,000), the newspaper said, citing a statement to Arabic-language media.
Since the diplomatic row erupted, slogans against and in support of Qatar have been among the top topics discussed on Twitter in Arabic, which is a hugely popular medium of expression in the Arab world, particularly in Saudi Arabia.
Newspapers and television channels in the region have also been engaged in a war of words over Qatar's role.
