The Gulf has entered a new era of instability. If its leaders think they can rely on old alliances, they are wrong | Nesrine Malik

The latest attack by Houthi rebels on Saudi Arabia may prove to be more calamitous for the region than the world imagines

On Saturday, Houthi rebels launched a shocking and deadly attack on Saudi Arabia's capital city, Riyadh. At the time of writing, the missile strike on King Khalid international airport has killed at least 13 people and left 300 injured, marking a significant turn in a regional conflagration that is only getting more intense. It was the single most deadly attack on any Gulf country since the US and Israel launched their war on Iran in February. In Saudi Arabia, a country that is unaccustomed to such fatalities, the death toll is bewilderingly high and likely to prompt a bloody response.

Over the past year, the Gulf has entered a new era of instability that is not temporary and cannot be reversed. This may feel like an overstatement - casualties have been relatively low, after all, compared with Gaza and Iran - but the gradual erosion of peace and security in places such as Saudi Arabia, Qatar and the UAE has changed the region more dramatically than its leaders would like to acknowledge.

Nesrine Malik is a Guardian columnist