Saudi air defences destroyed a drone south of Mecca on Tuesday evening, setting off the first security alerts in the city since the Middle East war began, as Houthi forces extend their control of Yemen's Red Sea coast and the Bab el-Mandeb strait at its southern end.

Major General Turki al-Malki, spokesman for the Saudi-led coalition, said the drone was intercepted before it entered prohibited airspace and that the security of the holy city was "a red line". A Houthi military source quoted by the group's SABA news agency denied the Houthis posed any threat to Mecca, saying they target oil facilities and military bases. The Organisation of Islamic Cooperation condemned what it called a "heinous" Houthi attack.

On the ground in Yemen, the Houthis took the port of Mokha and Mayun island, inside the strait, last week, then Greater and Lesser Hanish islands about 160 kilometres to the north. Officials of Yemen's Saudi-backed government have acknowledged the Houthis now control almost the entire western coast along the Red Sea. The 2022 truce that had largely quietened the war has not survived September.

Houthi military spokesman Yahya Saree said on Wednesday the group had fired drones and missiles at the Saudi oil port of Yanbu and the Khamis Mushait air base, and claimed Saudi Arabia had carried out as many as 450 air strikes on Yemen this week. Riyadh has not confirmed its strikes, though officials in the Yemeni government have acknowledged them. A Houthi claim to have shot down a Saudi-led coalition F-15 over Marib has not been verified.

The Red Sea matters more than usual because the Gulf's other exit is already choked. The Associated Press puts current flows through the Strait of Hormuz at an estimated 5 to 7 million barrels a day, against 15 million before the US-Iran war began on 28 February. Saudi Arabia's East-West pipeline, which moves crude across the kingdom to Yanbu on the Red Sea, has been out of action since an attack Riyadh blamed on Iran-aligned militias in Iraq. Regional officials told AP repairs could take three to five weeks; US Energy Secretary Chris Wright has said oil should flow within days.

Brent crude traded around US$108 a barrel on Wednesday, near its highest level since May.

Two regional officials told AP that Saudi Arabia, short of missile interceptors as US stocks run down over the Iran war, had asked France, Britain, Pakistan and Egypt for air defence support. Saudi Arabia has not confirmed that. Turkish and Pakistani officials said they had received no request under their new defence pact with Riyadh, and a spokesman for the British Prime Minister would not say whether one had been made.

In Beijing, Chinese Foreign Minister Wang Yi told Iran's Foreign Minister Abbas Araghchi that China "does not wish to see regional tensions further spill over into Yemen and the Red Sea", according to the Xinhua readout, and urged the reopening of Hormuz. Araghchi said Iran regarded its memorandum of understanding with the US, agreed in Islamabad, as still valid. UN Secretary-General António Guterres, briefing reporters ahead of next week's General Assembly, urged all parties to respect navigation through Hormuz and the Bab el-Mandeb. "The only path forward is de-escalation, diplomacy and dialogue," he said.

The casualty counts measure different things and are not interchangeable. The World Health Organization, as reported by AP on 15 September, said more than 500 people had been killed in Yemen in the previous week and nearly 94,000 displaced. The UN human rights office had verified at least 40 civilian casualties, eight killed and 32 injured, between 3 and 14 September.

For Australians, the cost arrives at the bowser. NRMA figures reported on 12 September put the average price of regular unleaded at $2.11 a litre, up from $1.55 in July, with the temporary fuel excise cut having ended on 2 August. Smartraveller advises Australians to reconsider their need to travel to Saudi Arabia and not to travel within 30 kilometres of the Yemen border. The federal government had made no public statement on the Mecca interception or the Red Sea escalation as of Thursday morning.

There is no ceasefire in the US-Iran war, and none in Yemen. World leaders gather at the UN General Assembly from Tuesday.