Tension has sparked global concern, as Bahrain, Sudan and Kuwait severe relations with Teheran

Tensions between Saudi Arabia and Iran erupted into a full-blown diplomatic crisis as Riyadh and its Sunni Arab allies cut or reduced ties with Teheran, sparking global concern.

Following angry exchanges over Saudi Arabia's execution on Saturday of prominent Shiite cleric and activist Sheikh Nimr al-Nimr, Riyadh and then Bahrain, Sudan and Kuwait severed relations with Teheran, the main Shiite power.

China, European countries and Turkey voiced concerns over the row.

"At present, the situation in the Middle East is complex and uncertain," Foreign Ministry spokeswoman Hua Chunying said on Tuesday.

The UN envoy for Syria headed to Riyadh and Teheran to defuse tensions, and a US official said Washington was "urging calm and de-escalation".

The crisis has also raised fears of an increase in sectarian violence in the Middle East, including in Iraq where two Sunni mosques were blown up late on Monday.

Saudi Arabia cut ties with Iran late on Sunday, giving diplomats 48 hours to leave the kingdom after protesters set fire to its embassy in Teheran and a consulate in Mashhad, an attack strongly condemned by the UN Security Council.

Envoys recalled

Bahrain and Sudan followed suit on Monday, and the United Arab Emirates and Kuwait also recalled their envoys from Teheran.

Sunni Arab nations accuse Teheran of repeatedly meddling in their affairs, with Saudi Foreign Minister Adel al-Jubeir saying "Iran's history is full of negative interference and hostility in Arab issues".

Iran denounced the Saudi moves as tactics that would inflame regional tensions.

Iran's President Hassan Rouhani, a moderate, on Tuesday said Riyadh cannot hide "its crime" of executing the cleric by cutting ties with Teheran.

About 3,000 demonstrators rallied in Teheran on Monday.

In Shiite-majority Iraq, top cleric Grand Ayatollah Ali al-Sistani called Nimr's execution "an unjust act of aggression", and on Monday blasts rocked two Sunni mosques, wounding at least three.

AFP - Reuters - AP - Xinhua