The good news: Iranian-backed Houthi rebels have temporarily stopped firing missiles at US Navy ships off the coast of Yemen. The very, very, very bad news: They’re now aiming them at Mecca.

Good thing this isn’t a volatile region, or something bad might happen. Oh, wait …

Yemen’s Houthi militia launched a ballistic missile toward Mecca on Thursday, the Saudi-led coalition intervening in Yemen’s civil war said on Saudi state news agency SPA.

Coalition forces destroyed the missile 65 km (40 miles) from the holy city without damage and retaliated against the launch site inside Yemen, the statement said. Mecca is home to the most sacred sites in Islam, including the Grand Mosque.

It’s no secret that Iran backs the Houthi rebels in Yemen in an attempt to extend its hegemony in the region. The Saudis have backed the recognized Yemeni government, and the US has backed the Saudis, in part on the basis of the Iranian proxy fight but also because the previous government partnered with us against al-Qaeda in the Arabian Peninsula (AQAP). Thanks to the civil war in Yemen, AQAP has had plenty of opportunities to expand their footprint locally and to plot terror attacks globally. The Saudis and the US have lots of incentives to reimpose order, but the Iranians have just as many to sow chaos.

And there isn’t much doubt where the Houthis have acquired ballistic missiles, either:

U.S. officials tell NBC News that they believe Iran has supplied weapons to the Houthis in Yemen — including coastal defense cruise missiles like the ones that were fired at US Navy ships earlier this month.

“We believe that Iran is connected to this,” Vice Admiral Kevin Donegan said.

The head of U.S. Naval Forces Central Command, who is tasked with securing the waters off of Yemen, disclosed today that the U.S. and partner nations have intercepted five weapons shipments from Iran that were headed to the Houthis in Yemen.

Clearly this fight in Yemen has become a proxy fight between the leading Shi’ite nation of Iran and Saudi Arabia, the most powerful Sunni nation in the region. On top of the sectarian issues, Mecca itself has become a flashpoint in the tensions between the two nations. Five months ago, Iran barred its subjects from making the hajj, the pilgrimage to Mecca and Medina required of every able-bodied Muslim at least once, accusing the Saudis of cyberwar but also of being incompetent stewards of the holy sites. Of course, that argument might lose a little of its moral force with Iranian ballistic missiles being aimed at Mecca.

This represents a serious escalation. If the Houthis are aiming missiles at Mecca, this proxy war steps dangerously close to being an actual war. The Saudis might rise to the bait, too, if they’re convinced that Iran will acquire nuclear weapons in the not-so-distant future, figuring that now would be a good time to settle it without mushroom clouds where Riyadh used to be. An attack on Mecca might wind up isolating Iran and generating a broader alliance for the Saudis against Iran, too, if the Saudis escalate. On the other hand, the Saudis have lots of reasons to avoid war too (it rhymes with schmollars), and perhaps the fact that they easily swatted the missile down will allow them to de-escalate. This has the potential to light the fuse on a long-pent-up explosion, one that will produce outcomes that neither the Saudis nor Iranians can predict.