Saudi Arabia has threatened to block Qatar by land and sea unless it cuts ties with the Muslim Brotherhood, shuts down broadcaster Al Jazeera and expels local branches of two US think tanks, according to US-based Huffington Post.
The threats were made during a private meeting between the foreign ministers of the six Gulf Cooperation Council states in Riyadh last week - before the kingdom, the UAE and Bahrain withdrew their ambassadors from Doha, a source who was present at the meeting said.
Saudi foreign minister Saud bin Faisal reportedly said only those three requirements would be sufficient to prevent Qatar from "being punished".
Days later the Gulf state was left embarrassed by the departure of ambassadors from the three neighbouring countries historically close to Qatar.
On Friday, Saudi Arabia also declared the Muslim Brotherhood a terrorist organisation, following the same decision taken in Egypt in December.
The two US think tanks targeted are the Brookings Doha Centre and the Rand Qatar Policy Institute, while Al Jazeera has been accused of deliberate bias towards the Muslim Brotherhood in its reporting on the conflict in Egypt as well as playing a significant role in the ousting of leaders in Tunisia and Egypt during the Arab Spring.
Three journalists from Al Jazeera English have been detained since late 2013, accused of joining a terrorist group, aiding a terrorist group, and endangering national security. A fourth journalist, from Al Jazeera Arabic, Abdullah Al Shami has been held for six months and is being tried in a separate case.
Saudi Arabia and the UAE have spent $32bn supporting Egypt's military government post-Brotherhood. Former president Mohamed Morsi was deposed in July last year but there is no real end to the conflict in sight.
Saudi Arabia and Qatar share about 64km of sea and land borders and there have been clashes in the past. The borders were disputed for 35 years and a final agreement was only signed in 2001.
Qatar is not taking the threat of a sea blockade seriously, according to the Huffington Post. But the land border – across which a substantial amount of food and goods flows to the Qatari capital Doha – can be easily closed by the kingdom.
Several Saudi and Emirati journalists also have quit their jobs in Qatari media following calls to do so by their governments.
The diplomatic dispute is unprecedented between the GCC members, who otherwise had been working to form closer economic and security ties.