For years just an obscure fight raging in remote desert mountains, Yemen's war with Shiite rebels has been dragged up to a new level, inflaming the rivalry between the Middle East's two powerhouses Saudi Arabia and Iran.
That rivalry has encompassed nearly every conflict in the region: In Lebanon and Iraq and among the Palestinians, Iran has backed militant groups, and U.S. ally Saudi Arabia has supported its own proxies to counter them, fearing the spread of Tehran's power in the region.
Now Saudi Arabia is waging a heavy military assault against the Shiite Yemeni rebels on its border, warning of a new attempt by Tehran to spread its power.
It isn't certain Yemen's tiny but bloody war actually belongs in the same category as other Iran-Saudi flashpoints. Saudi Arabia and Yemen accuse Iran of sending weapons to the Shiite rebels, known as the Hawthis, and trying to bring the area into its sphere of influence.
But they have not given credible proof of their claims, which Tehran denies. Many outside experts are skeptical Iran has a role. Washington has not backed the Saudi and Yemeni accusations and has focused more on an entirely different front _ pressuring Yemen to act more strongly against al-Qaida's increasing presence on its territory.
Nonetheless, in recent weeks, the conflict in northern Yemen has sharply heightened the hostility between Saudi Arabia and Iran _ and that could raise tensions in the other conflicts between the two nations.
Both countries sent warships off Yemen, putting their navies in close proximity. Officials and powerful clerics in both Iran and Saudi Arabia have stepped up their rhetoric to more feverish levels. Iran's parliament speaker accused Saudi Arabia of crimes against the rebels. Saudi Arabia's most senior cleric last week railed against Iran, saying it and the rebels are in a "collaboration of sin and aggression."
Saudi TV footage and newspaper reports meanwhile have been filled with stories about Saudi military might, while columnists and political analysts have been making dire warnings of Iran's intentions.
"If the Iranians establish a foothold in the Arabian Peninsula, the Arab world is finished," analyst Khaled al-Dakhil told The Associated Press, accusing Iran of seeking to turn the rebels into another Hezbollah, the Lebanese Shiite militant group that spearheaded the border fight with Israel.
"The Hawthis' domestic case may be legitimate, but when they become a card to be used by Iran in the region _ that is not acceptable," he said.
Yemen's central government has been fighting the Shiite Hawthis for nearly five years, one of multiple ongoing conflicts in the unstable, impoverished nation on the southern tip of the Arabian Peninsula. Fighting escalated dramatically earlier this year, with Yemeni warplanes frequently bombarding the rebel's stronghold region of Saada, near the Saudi border.
While backing the Yemen government, Saudi Arabia avoided direct involvement _ until Shiite rebels crossed into the kingdom and killed a Saudi soldier.
The Saudis unleashed a heavy offensive that is still ongoing, including relentless artillery bombardment and air raids against the Hawthis. The rebels claim that Saudi forces have struck inside Yemen, though the Saudis insist they have focused solely on driving the Hawthis back across the border.
Saudi warships deployed off of Yemen's western Red Sea coast to prevent weapons and fighters from reaching the rebels. Authorities have also evacuated more than 400 Saudi villages near the border, a first step toward creating a cordon inside the kingdom to control who can come in.
Iran, on the other hand, has sent its own fleet of ships to Yemen's other, southern coast, on the Gulf of Aden, ostensibly to defend Iranian shipping against attacks by Somali pirates. On Sunday, Yemen's Interior Ministry reported that an Iranian ship had stopped, searched and interrogated a Yemeni fishing vessel.
Tehran's leaders have also lashed out at Saudi Arabia. Parliament speaker Ali Larijani described the Saudi actions as "suppressive" and criticized King Abdullah for waging "a military operation to shed the blood of Yemeni Muslims" so close to this week's annual hajj pilgrimage, a symbol of Muslim unity.
Some 250 Iranian members of Parliament have signed a petition condemning the Saudi "crime."
Iranian media have been reporting extensively on the suffering of Yemeni Shiites, hundreds of thousands of whom have been driven from their homes in the fighting.
Iran often poses as the patron of Shiites around the region. At the same time, Sunni-led nations like Saudi Arabia are eager to stop any sign of increasing Iranian influence. The rise of Iranian-backed Shiite parties in Iraq has raised Arab fears that that country _ once ruled by Sunnis _ will end up under Tehran's sway. Iran's Hezbollah allies in Lebanon have clashed repeatedly with Saudi-backed Lebanese groups. Hamas in the Gaza Strip and restive Shiites in Bahrain have also been accused of receiving Iranian backing.
The tensions between Iran and Saudi Arabia over Yemen could spill over into an escalation in the other hot spots _ at a time of deadlock in U.S.-backed Mideast peace efforts, rising tensions between Iran and the West over its nuclear program and fears of an Israeli strike against Iranian nuclear facilities.
Iranian analyst Mashaallah Shamsolvaezin believes Tehran does not intend to get directly involved in Yemen, however. Doing so "will only lead to an increase in the Western presence in the Gulf" as Arab governments seek help, said Shamsolvaezin, an adviser to the Middle East Strategic Studies Center, a Tehran think tank.