A UN watchdog on Monday hailed a letter by nearly a dozen Arab nations that accuses Iran of sponsoring terrorism throughout the Middle East, and of ramping up its support of jihadist groups since the signing of its nuclear deal with the US-led P5+1 nations last year.

The October 27 letter to outgoing UN Secretary General Ban Ki-moon cautioned that Iran “continues to play a negative role in causing tension and instability in our region,” and cited Tehran’s “expansionist regional policies, flagrant violations of the principle of sovereignty and constant interference in the internal affairs of Arab States.”

The letter was signed by the UN ambassadors of Bahrain, Egypt, Jordan, Kuwait, Morocco, Oman, Qatar, Saudi Arabia, Sudan, United Arab Emirates and Yemen.

“We stress that the Islamic Republic of Iran is a State sponsor of terrorism in our region, from Hezbollah in Lebanon and Syria, to Houthis in Yemen and terrorist groups and cells in the Kingdom of Bahrain, Iraq, the Kingdom of Saudi Arabia, Kuwait and elsewhere,” the countries wrote.

The Arab countries charged the Islamic Republic “calls for the export of its revolution to other countries” through its religious and political leaders.

Members of Lebanon's Shiite movement Hezbollah hold their flags during the funeral of a Hezbollah fighter, who was killed while fighting alongside Syrian government forces in Syria, March 1, 2016. (AFP/MAHMOUD ZAYYAT)

Members of Lebanon’s Shiite movement Hezbollah hold their flags during the funeral of a Hezbollah fighter, who was killed while fighting alongside Syrian government forces in Syria, March 1, 2016. (AFP/MAHMOUD ZAYYAT)

“Unfortunately, since the signing of the nuclear deal, we have seen nothing but increased Iranian aggression in the region and the continuation of support for terrorist groups,” the letter said.

UN Watch, a Geneva-based monitoring group, welcomed the letter, saying it was “important” that Muslim Arab countries were speaking out against Iranian policies.

“Iran likes to dismiss all criticism of its human rights violations and brutality at home and abroad as part of a western plot, but that’s hard to sustain when the accusers are all Muslim governments, including recent allies of Iran like Sudan,” said UN Watch director Hillel Neuer in a statement.

Relations between Iran and some Sunni Arab countries have deteriorated in recent years over Tehran’s involvement in regional conflicts.

Saudi Arabia and its allies have condemned Iran’s military support of Hezbollah, a Lebanon-based terrorist group that has intervened in the Syrian way to support Assad.

Saudi Arabia backs rebels opposed to Syria’s government.

In 2015, Saudi Arabia launched an Arab coalition supporting Yemen’s government fighting the Iran-backed Houthi rebels which seized the country’s capital and other areas.

Riyadh cut diplomatic ties with Tehran earlier this year after demonstrators burned its embassy and a consulate following the Saudi execution of a prominent Shiite cleric.