1979: Iranian revolution

• Sunni-ruled Saudi Arabia watches aghast as Iran's King Shah Mohammed Reza Pahlavi is ousted by Shi'ite Muslim clerics in what is called the Islamic Revolution.

1980-1988: Iran-Iraq war

• Iran fumes over Saudi support for Iraq during the Iran-Iraq war.

1987: Mecca clashes

• 402 pilgrims, 275 of whom were Iranian, die during clashes in the Muslim holy city of Mecca, leading to protests in Teheran and the occupation of the Saudi Embassy, where a Saudi diplomat dies.

• Saudi Arabia's King Fahd severs diplomatic relations in 1988.

1997-2001: Better times

• Saudi Crown Prince Abdullah visits Iran for a summit in 1997.

• Iranian President Mohammad Khatami visits Saudi Arabia in 1999, the first visit by an Iranian president since the revolution. The nations seal a security pact in 2001.

2003: Regional rivalry

• The United States' invasion of Iraq empowers the country's Shi'ite majority.

• Iran's nuclear programme deepens Saudi fears that President Mahmoud Ahmadinejad is bent on dominating the Gulf.

2011: Arab Spring

• Saudi Arabia sends troops to help Bahrain quash pro-democracy protests. •After Shi'ites clash with the police, Saudi Arabia accuses them of cooperating with Iran.

2012: Proxy war

• Saudi Arabia becomes the main supporter of rebels fighting to topple Syrian President Bashar al-Assad, an ally of Iran.

2015: Another low point

• Iran's Supreme Leader demands the Saudis apologise for Mecca stampede.

• Saudi Arabia cuts diplomatic relations with Iran over the storming of the Saudi Embassy in Teheran.

REUTERS