CAIRO: Saudi Arabia on Tuesday imposed a naval blockade on the Red Sea coast of northern Yemen to combat Shiite rebels along its border, an adviser to the government said, in the latest escalation of fighting in the southern Arabian peninsula.

The Saudi move comes as Iran, the region's dominant Shiite power accused by the Arabs of backing the rebels, warned neighboring countries not to interfere in Yemen's internal affairs.

The adviser said Saudi warships had been ordered to search any suspected ship sailing near the Yemeni coast. He spoke on condition of anonymity because he was not authorized to speak to the media.

Saudi-owned Al-Arabiya satellite television also reported the blockade.

Shiite rebels in northern Yemen, known as Hawthis, have been fighting the Yemeni government for the past five years, but in recent months the violence has flared up and even crossed the border into Saudi Arabia.

The blockade comes after several days of Saudi airstrikes against the rebels, which continued Tuesday.

Prince Khaled bin Sultan, the assistant defense minister, said Tuesday the rebels must "withdraw dozens of kilometers" inside Yemen before the Saudi army would halt its assault.

Both Yemen and Saudi Arabia have been accusing Iran of sending weapons and money to the Shiite rebels. Iran denies the charge and even warned against outside involvement in the impoverished country.

"The regional countries and especially the neighboring countries, we recommend seriously they not interfere in the internal issues of Yemen and instead try to restore stability in Yemen," said Iranian Foreign Minister Manochehr Mottaki on Tuesday.

The offensive has immediately raised concerns of another proxy war in the Middle East between Iran and Saudi Arabia, a key U.S.

ally. Shiite Iran is believed to favor the rebels in Yemen while Saudi Arabia, which is Sunni, is Iran's fiercest regional rival.

The same dynamic has played out in various forms in Lebanon, where Iran supports the Shiite militant Hezbollah and Saudi Arabia favors a U.S.-backed faction, and in Iraq, where Saudi Arabia and Iran have thrown support to conflicting sides in the Sunni-Shiite struggle.

For their part, the Hawthis have denied being backed by any of the regional players.

"We have no connection with any foreign side," said Yemeni rebel leader Abdel-Maliki al-Hawthi, in an audio statement sent to news agencies Tuesday.

The rebels also confirmed that Saudi air strikes were continuing, saying new villages had been hit deep inside Yemen, killing two women.