Dubai’s main share index was down around 2%, LSEG data showed, while Abu Dhabi’s main index dropped 0.9% and Saudi Arabia was down 0.6%.

Saudi Arabia said its national security was a red line, hours after a Saudi-led coalition launched strikes on what it described as foreign military support to UAE-backed southern separatists in Yemen, and also asked UAE forces to leave the country.

The Dubai index was on course for its biggest daily decline since June. Blue-chip developer Emaar Properties fell 3.5%, and top lender Emirates NBD was 1.7% lower.

Among Saudi shares, Al Rajhi Bank eased 0.7% and Saudi National Bank, the country’s biggest lender by assets, retreated 1.1%. Oil giant Saudi Aramco was down 0.3%.

Oil prices - a catalyst for the Gulf’s financial markets - were little changed after Russia accused Ukraine of attacking President Vladimir Putin’s residence and investors sought clarity on Ukraine peace talks to gauge potential supply disruptions.

The Qatari index was down 0.4%, with Qatar National Bank, the Gulf’s biggest lender, dropping 0.7%.

Bahrain bucked the trend with a 0.4% rise after the country implemented several fiscal reform measures on Monday.