CAIRO, Egypt: Yemen's Iranian-backed Houthi rebels have captured two more strategic islands in the southern Red Sea, according to Yemeni government and Houthi officials. The move strengthens the rebels' control over an important global shipping route.

The Houthis captured the islands of Greater Hanish and Lesser Hanish after Saudi-backed government forces tried over the weekend to regroup and stop the rebels' rapid advances around the Bab el-Mandeb Strait. The narrow waterway is a key shipping route and an alternative to the Strait of Hormuz.

Meanwhile, Iran said that Saudi Arabia was behind Oman's decision to postpone a meeting bringing together Iran with other regional countries to discuss the Strait of Hormuz.

The Houthis' recent territorial gains around Bab el-Mandeb are their biggest in several years. The expansion could support Iran's efforts to push up global oil and gas prices and increase pressure on the United States.

The new Houthi positions also give the rebels greater ability to threaten Saudi oil shipments. Saudi Arabia has used the Red Sea to move crude as an alternative to routes through the Strait of Hormuz, where Iran has been attacking shipping.

The growing conflict, particularly possible Houthi attacks on Saudi oil facilities and ships in the Red Sea, is increasing concerns about global energy supplies. Higher oil prices could give Iran additional leverage in its war with the United States.

Two Yemeni government officials and a Houthi official said the rebels sent fighters to the Hanish islands, about 160 kilometers (100 miles) north of Bab el-Mandeb. The move followed the withdrawal of hundreds of fighters allied with Yemen's internationally recognized government. The officials spoke anonymously because they were not authorized to speak to the media.

The latest capture followed the Houthis' seizure last week of the nearby mainland port city of Mokha and Mayun island, which lies inside the Bab el-Mandeb Strait. Their advance has also brought them within about 32 kilometers (20 miles) of the US military base in Djibouti, located on the opposite side of the strait.

The Houthis faced little resistance from forces loyal to the internationally recognized government. However, government forces tried to regroup over the weekend. Yemen's military said late on September 13 that its forces had moved towards the strategic town of Dhubab, north of the strait.

The latest fighting is threatening to push Yemen back into a full-scale civil war. The country had remained relatively calm for about three years under a truce that largely reduced fighting between the main sides.

The developments around Bab el-Mandeb are also raising wider concerns because the waterway is a major route for international trade and energy shipments. Any prolonged disruption could affect shipping costs and add pressure to already sensitive global oil markets.

Meanwhile, China, a major importer of oil from the Middle East, condemned Houthi attacks on Saudi Arabia's energy infrastructure and said it was deeply concerned about the possibility of further attacks by the Iran-aligned rebels.

Chinese Foreign Ministry spokesperson Guo Jiakun said attacks on civilian infrastructure that is important to people's daily lives could not be accepted.

"Attacks on civilian infrastructure that is important to people's livelihoods are unacceptable," Guo said.

He urged all sides to show restraint and avoid further escalation. China also called on the parties involved to settle their disputes through dialogue and peaceful negotiations.