President Donald Trump vowed Monday to hold Iran responsible after fighting between the United States and Houthi militants escalated following U.S. airstrikes over the weekend.

President Trump said Monday he would hold Iran responsible for any future attacks by the Houthis in Yemen, threatening unspecified consequences against the Islamic Republic after he ordered large-scale strikes in recent days against the militants.

Houthi leader Abdul Malik al-Houthi said his militants would continue to target American ships in the Red Sea as long as the U.S. attacks Yemen, warning, 'If they continue their aggression, we will continue the escalation.

Oil futures climbed on Monday, finding support after the U.S. over the weekend launched U.S. strikes on Houthi rebels in Yemen, raising the risk of disruptions to oil flow in the region.

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.