Saudi Arabia said on Friday it had intercepted a Houthi drone attack on a shipping vessel as the rebel group announced it had made military gains across central Yemen. The Saudi Arabia-led coalition battling the Houthi rebels in Yemen said it had thwarted an attempted drone strike on a Saudi commercial ship, without offering further details, the state-owned Al Arabiya outlet reported. The Houthis meanwhile confirmed on Friday that they had seized two districts in central Al Bayda province, <a href="https://www.thenationalnews.com/gulf-news/2021/07/29/yemens-houthis-increase-attacks-in-bid-to-seize-marib/" target="_blank">amid continued fighting for control of nearby Marib, a strategic government-held area for oil and gas production</a>. Houthi military spokesman Yahya Saree described the “liberation of the Naman and Nateh districts” in Al Bayda, a statement carried by the rebels' Al Masirah television network said. Details of further Houthi advances were expected to be announced on Saturday. Gains by the Iran-backed Houthis in the regions of Al Bayda and Shabwa raise the prospect of the rebels gaining control of Marib, the Saudi-backed government’s last remaining stronghold in northern Yemen. The Houthis in February ratcheted up their efforts to seize Marib, where clashes have killed hundreds on both sides. Control of the oil-rich region would bolster the Houthis' bargaining position in future peace talks. A study by research group Acaps this week said <a href="https://www.thenationalnews.com/world/us-news/2021/07/26/houthi-win-in-marib-would-compound-yemens-refugee-and-economic-crises/" target="_blank">a Houthi victory in Marib could displace half a million more people and deal a fatal blow to Yemen’s exiled government</a> by robbing it of $19.5 million each month in lost crude sales. UN spokeswoman Eri Kaneko urged both sides to return to negotiations, lay down their weapons and let aid workers gain access to the millions of Yemenis who have been forced to flee their homes and need assistance to survive. “It just underscores the need to end this fighting so that we can get aid to those who need it the most,” Ms Kaneko said in answer to a question from <i>The National.</i> Yemen has been ravaged by war, disease and hunger since the Houthis seized the capital Sanaa and overthrew the government in 2014, drawing in a Saudi-led coalition the following year to restore the ousted leadership. The war has forced millions of Yemenis to flee their homes, claimed hundreds of thousands of lives and tanked the economy. Four fifths of Yemenis rely on aid, in what the UN calls the world's worst humanitarian crisis.