Saudi Arabia is trying to set up a buffer zone inside Yemen after its week-long offensive against the Yemeni Shiite insurgents along the border, a rebel spokesman said Wednesday.

Mohammed Abdel Salam said Saudi warplanes and artillery have been shelling deep into border areas to create the zone and drive the rebels away.

"Their goal seems to be establishing a buffer zone or a no man's land on the border," he said in a telephone interview from the rebels' strongholds in Yemen's northern Saada province. "It is obvious, they are trying to scare us and make us leave the area."

Saudi Arabia launched an air and ground offensive against the Yemeni rebels last week after skirmishes along the border. Both Saudi Arabia and Yemen have accused Shiite Iran of backing the rebels raising concerns of another proxy war in the Middle East between region's Shiite and Sunni powers.

Iran has denied the charge and warned against outside involvement in the impoverished Arabian Peninsula country. Iranian Foreign Minister Manochehr Mottaki said Tuesday regional countries should not "interfere in internal issues" in Yemen.

In San'a, the Foreign Ministry acknowledging Iran's comments and stressed in a statement Wednesday that no country has the right to interfere in Yemen's internal affairs.

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

Abdel Salam described the Saudi bombardment as "random" and hitting residential areas.

The Yemeni army has also halted its four month-long offensive on the rebels positions after the Saudi assault, he said. "They are leaving the Saudis to do the job for them now."

The official Yemeni news agency, Saba, said earlier that the army has advanced into some rebel-controlled areas and inflicted "huge casualties" on the insurgents.

Yemen has been embroiled in a sporadic, five-year conflict with Shiite rebels in northern Saada province along the border with Saudi Arabia. The Shiites accuse authorities of neglecting their needs and of allying with hard-line Sunni fundamentalists.

Fighting has intensified since August, displacing tens of thousands of people and limited their access to humanitarian aid.

According to the U.N.'s refugee agency, some 175,000 people have been displaced since the fighting began.

On Tuesday, a Saudi government adviser said Saudi army had imposed a naval blockade on the Red Sea coast of northern Yemen to stem the flow of weapons and fighters to Shiite rebels along its border.

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

On Wednesday the state news agency reported that Yemen has signed a military cooperation agreement with the United States for "exchanging experiences, training and qualification in the military and security fields."

Abdel Salam, the rebel spokesman, also predicted the buffer zone won't prevent infiltrators from Yemen — the most impoverished Mideast nation — from crossing into Saudi Arabia. He suggested many of those who cross are destitute Yemenis in search of a better life on the other side of the boundary.

"Poor Yemenis will keep crossing," Abdel Salam said.