RIYADH, Saudi Arabia (AP) — Yemen's Shiite rebels attacked Saudi border posts, sparking fierce fighting overnight that killed three Saudi troops and dozens of rebels, the kingdom said. Saudi-led airstrikes continued to bomb rebel positions inside Yemen on Friday, including a strike in the capital, Sanaa, that killed at least 20 civilians.
The attack late Thursday by the rebels, known as Houthis, was the most dramatic border incident since Saudi Arabia launched an intense campaign of airstrikes against the rebels just over a month ago. It also brought to 11 the number of Saudi soldiers killed so far in border skirmishes during the air campaign.
The assault underscored how the Iran-backed Houthis are still capable of launching major operations despite the airstrikes that have relentlessly targeted their positions and those of their allies — military units loyal to former president Ali Abdullah Saleh.
The Saudi-led offensive, which started March 26, aims to diminish the military capabilities of the Houthis, who have overrun the Yemeni capital, Sanaa, and are advancing deep into the country's south.
The U.N. says at least 550 civilians have been killed so in the war, whether from airstrikes or ground fighting.
Yemen's internationally recognized President Abed Rabbo Mansour Hadi, who fled the country in March, is now based in the Saudi capital of Riyadh, along with most of his government. There have been recent calls by officials in exile for a Saudi-led ground invasion to restore Hadi's government to power.
"There must be a direct military intervention ... to stop Saleh and the Houthis," Yemen's Transportation Minister Mohammed Badr Bassalma told Al-Arabiya satellite TV on Friday, speaking from Riyadh.
Also Friday, the U.N. Security Council held an emergency meeting on Yemen, following warnings by U.N. chief Ban Ki-moon who said the previous day that basic services in the impoverished Arab country are "on the brink of collapse." Ban also called for an immediate ceasefire, or at least humanitarian pauses to help the desperate civilians.
The meeting, however, ended with the 15 Security Council members unable to agree on an immediate statement on the growing crisis.
There have been conflicting figures on the death toll since the air campaign started. Ban's office said Thursday that more than 1,200 people have been killed in the conflict, which has turned into a kind of proxy war between Yemen's powerful neighbor Saudi Arabia and Iran. Many of those dead have been civilians. Hadi's government in exile says at least 1,000 civilians have died.
On Friday, the Saudi-led coalition continued to pound rebel positions. One airstrike targeted a house of a top Houthi rebel commander in Sanaa's Saawan district, demolishing at least six houses and killing at least 20 civilians, including 10 women and children, officials and witnesses told an Associated Press reporter at the scene.
In the southern port city of Aden — Hadi's base before he fled to Riyadh— and in the city of Taiz, warplanes bombed positions of the Houthis and Saleh's forces killing scores of fighters, according to security officials. At least 12 people were killed because of ground fighting in Aden on Friday, according to medical officials who did not elaborate. All officials spoke on condition of anonymity because they were not authorized to talk to the media.
In the border attack, Houthi fighters in tanks and armored vehicles struck "border posts and control points" in the southern Saudi region of Najran on Thursday night, the kingdom's Defense Ministry said.
Saudi forces, backed by fighter jets, repelled the attack and "dozens of the militiamen were killed. Three soldiers of the ground troops were martyred," according to the statement, which did not clarify how far across the border the attackers came.
The kingdom's security forces said on April 11 that more than 500 Houthi rebels have been killed in border clashes, mostly in the area of Najran. The kingdom has offered the families of each slain soldier 1 million Saudi riyals, or about $267,000, to compensate for their loss.
Since the airstrikes began, Saudi Arabia boosted its troop numbers along the roughly 1,300 kilometers (800 miles) long border with Yemen. The troops frequently fire at suspected rebel positions with both cannon and mortar fire.
The area across the border is considered a Houthi stronghold. The Houthis managed to take several scattered Saudi villages in the southern border region of Jizan in 2009, during the kingdom's last war with the rebels.
Last week, during an AP trip to Saudi military positions in Jizan and Najran, the commander of Najran forces, Brig. Gen. Abdullah al-Shehri, said the border situation was stable. The war has so far not included a ground force operation in Yemen but al-Shehri said his forces were prepared for any eventuality.
Despite more than a month of airstrikes, the campaign has largely failed to halt the Houthis' advance on Aden.
But the Saudis say they have eliminated much of the stockpiles of missiles and heavy weapons that were allegedly under the control of Saleh's forces and his rebel allies. The kingdom says it has also succeeded in barring Iran from delivering more money and weapons to the Houthis.
Iran and the Houthis deny that Tehran has ever armed the rebels, but acknowledge humanitarian and political support from the Shiite nation.
Al-Haj reported from Sanaa, Yemen. Associated Press writer Cara Anna at the United Nations contributed to this report.