Yemen's years-long internal military conflict raging between the Houthi rebels and the country's government backed by Saudi Arabia witnessed a major turn and started to pose a real threat for the region's security and stability, experts said.

The Iran-allied Houthi rebels turned to launching attacks using numerous explosives-laden drones against vital institutions deep inside Saudi Arabia amid heightened tension between Iran and Saudi Arabia.

Two separate drone attacks on Saudi Arabia's Najran airport were claimed by the Houthi rebels within 24 hours and just a few days after launching similar coordinated drone attacks on two oil pump stations near Riyadh.

Yemeni experts believe that the escalation of the Houthi drone attacks indicate that the country's years-long conflict started in expansion far beyond the borders to include other neighboring countries in the region.

The professor of political sociology at the University of Sanaa Abdul Baqi Shamsan told Xinhua that the timing of the frequent Houthi drone attacks aimed at delivering obvious messages from Iran to its rivals in the region, particularly Saudi Arabia.

"It's obvious that Iran started to use its loyal proxies in the region, including the Houthi militias, for the purpose of hurting Saudi Arabia indirectly through simply manufactured drones," said Abdul Baqi.

During the past days, the Houthi Defence Ministry based in Sanaa showed a new defiance through declaring that the recent drone attacks came as the first batch of a large upcoming military operation that includes 300 targets against vital targets in Saudi Arabia and the United Arab Emirates (UAE).

The surprise development of the Houthis military capabilities and tactics raised a number of questions among Yemen's local observers following years of an intense aerial bombardment launched by the Saudi-led coalition against the rebels-held military locations across the country.

Brigadier Mohammed Jawas, strategic military expert based in the southern port city of Aden, revealed to Xinhua the major factors that helped Houthis to develop their military equipment despite the presence of the Saudi-led coalition in Yemen.

"The Saudi-led coalition succeeded in destroying the Houthi military capabilities but failed in tightening supervision and securing the borders of Yemen to prevent the operations of smuggling weapons and drones to the rebels from their foreign allies," said Jawas.

He expected that the Houthis' recent military escalation against Saudi Arabia may lead to serious consequences, including destabilizing the regional security and stability and promoting for imminent confrontation between rival powers in the region.

"Recently the region's situation is very tense and the United States imposed a series of sanctions on Iran that apparently resorted to using its Houthi proxies to attack the strategic allies of the U.S. in the region particularly Saudi Arabia," he said.

"The Houthi militias are playing a very dangerous game and attacking the strategic interests of the United States in the region may put the rebels in real military confrontation with America and the International Community," warned Jawas.

Washington and Tehran have been locked in a war of words over the past two weeks, and escalating tension that had been stoked up following America's increasing military buildup in the Middle East.

U.S. media reported on Wednesday that the Pentagon is expected to submit plans to the White House to send up to 10,000 troops to the Middle East amid increasing tensions with Iran.

Ali Hadi, another Yemeni military expert and observer, told Xinhua that Iran exploited its strong ties with the Houthis and deliberately pushed the rebels to step up their drone attacks against Saudi Arabia as a response for the ongoing U.S. escalation against Iran.

He said that "Iran is facing U.S. pressures and the increasing Houthi drone attacks on Saudi Arabia is considered as a warning message to Washington from the regime in the Islamic State that is trying to show its ability to expand the war to include the Gulf states."

On May 14, Houthi spokesman Mohammed Abdulsalam said on Twitter that the attack on Saudi oil facilities was a response to the Saudi attacks on his group, vowing Houthis' readiness to launch more such attacks.