Overnight strikes in Yemen have set off alarm bells in Saudi Arabia, which craves de-escalation in its war-torn neighbour so it can focus on domestic reforms, analysts said.Explosions lit up the night sky early on Friday as the United States and Britain pounded scores of targets with more than 100 precision-guided munitions, US Central Command said.The strikes came in response to weeks of disruptive attacks on Red Sea shipping by the Iran-backed Huthis, who control northern Yemen and say they are firing on Israel-linked ships in solidarity with Palestinians in Gaza.