The U.S. carried out new airstrikes on Yemen, expanding the biggest U.S. military operation in the Middle East since President Trump took office.

President Donald Trump announced he ordered the U.S. military to launch "decisive and powerful military action" against the Houthis in Yemen.

Yemen's Houthi rebels say there have been fresh US strikes against them, with the number of dead rising to 53, including five children. Targets in the Al Jaouf and Hudaydah areas were hit early on Monday, according to the rebel group, while the US Central Command said its forces had continued operations.

Oil traded higher on Monday after the United States vowed to keep attacking Yemen's Houthis until the Iran-aligned group ends its assaults on shipping, and Chinese economic data fuelled hopes for higher demand.

Oil prices were up nearly 1 per cent on Monday after the US bombed Yemen's Houthis for a second night, warning of an “unrelenting” attack on the militant group, and as China announced stimulus plans to boost its tepid economy.