Saudi Arabia said on Friday that its jets and ground forces had blasted Yemen rebel positions along the two countries' rugged frontier amid reports of casualties among the Saudi population in the area.
Sporadic shelling could be heard from the border around the Jebel al-Dukhan mountain and jets screeched overhead on Friday after two days of aerial bombing of the Zaidi rebels, according to an AFP photographer.
The air strikes from southern Jizan province were to "neutralise the firing by intruders" and to clear areas where they had encroached on Saudi territory, the government said in a statement on the official SPA news agency.
Earlier, a government adviser said Saudi F-15 and Tornado jets had bombed camps of the Zaidi rebels inside Yemeni territory on Wednesday and Thursday in response to a rebel attack on a border post a day earlier that left one Saudi border guard dead and 11 injured.
"We took back a small piece of territory and hit their camps around Saada," a rebel stronghold province over the border.
"They've been hit hard and it's ongoing," the advisor told AFP, adding that the move was taken with the knowledge of the Yemeni government.
It was the first acknowledged Saudi involvement in the Yemen government's three month campaign against the Shiite Zaidi rebels in the country's mountainous northwest corner.
The Saudi statement said it was responding to an incursion into its territory and attacks on its citizens, and said the counter attack was necessary to prevent the rebels from being able to fire into Saudi territory.
The London-based Saudi-owned newspaper Asharq al-Awsat reported that four Saudi women were killed when their border region home was shelled.
Other media reports said 40 of the rebels had surrendered to Saudi forces.
The SPA statement said government forces attacked rebel positions "inside Saudi territory" around Jebel al-Dukhan which straddles the border of Yemen and Saudi Arabia's Jizan province.
Residents were evacuated from villages around the 2,000 metre (6,600 foot) Jebel al-Dukhan when the fighting began and relocated to tent camps further away from the border, according to reports.
The adviser said the Saudi's attack came only after weeks of disturbances along the border, where Yemeni troops have been engaged in a three-month offensive against the Zaidi rebels, also known as Huthis after their late leaders.
The Yemen government accuses the rebels of seeking to restore the Zaidi imamate that ruled in Sanaa until its overthrow in a republican coup in 1962 that sparked eight years of civil war.
The fight has left hundreds dead or injured and sent tens of thousands of Yemenis fleeing their homes.
On Tuesday, a group of rebels entered Saudi territory and fired on border guards, killing one. They burned six vehicles and occupied two villages before being driven out by Saudi forces, according to the Saudi government.
Pictures on the local Jazannews.org website showed several Saudi village homes heavily damaged by alleged rebel mortar fire.
But the rebels accused the Saudis of permitting Yemeni troops to operate against them from inside Saudi territory.
Saudi Arabia's overt involvement has raised concerns among some experts that a "proxy war" is developing between regional rivals Riyadh and Tehran.
Yemen president Ali Abdullah Saleh -- who himself has Zaidi roots -- is heavily supported by the Saudi government. Meanwhile Sanaa accuses Iran of backing the rebels.
On October 28 Yemen said it had arrested five Iranians on a boat loaded with weapons allegedly destined for the Zaidis.
Late on Thursday, a US official said Washington was "concerned by the expansion of the conflict along the Saudi-Yemeni border."
"It's our view that there can be no long-term military solution to the conflict between the Yemeni government and the rebels," State Department spokesman Ian Kelly said.
