Yemen's Houthi rebels have claimed responsibility for a missile attack on the southern Saudi Arabia city of Jazan, marking a widening of conflict in the Middle East.Posting to Telegram on Saturday, the Houthis' Ansarollah media said a "Yemeni missile strike" had sparked fires in Jazan.Footage posted to social media suggested the Aramco oil refinery in the city had been hit.The Houthis had accused Saudi Arabia — a US ally — of a "dangerous escalation" after Riyadh struck military targets belonging to the Houthis on Friday, following the rebels announcing a maritime blockade of the top oil producer and hitting Riyadh's ships in the Red Sea.The Iran-backed group claimed attacks on two Saudi ships earlier this week, with Saudi Arabia confirming one of the attacks in the Red Sea.Riyadh did not immediately comment on the newest strikes, but its civil defence agency issued brief warnings to residents in the city, as well as Yanbu, earlier on Saturday.Greek security sources told Reuters that air defence systems in Saudi Arabia had intercepted two ballistic missiles from Yemen on Saturday, which were targeting oil refineries in Yanbu.Donald Trump says talks with Iran are continuing. (AP: Rod Lamkey Jr)Talks 'most serious that we've seen them'This flare-up marks a new front in a war that has engulfed the Middle East region following US-Israeli strikes on Tehran in February, and comes on top of Iran's parallel blockade of the Strait of Hormuz, Saudi Arabia's only other maritime route.The key waterway of the Strait of Hormuz, the entrance to the Gulf, has so far been the focus of a war that has killed thousands over almost five months, stoked global inflation and fanned fears of an economic downturn.The escalation came after US President Donald Trump said he would hold off on a major operation because Iran was now getting "serious" in talks with Washington.The US military broke its daily announcement of fresh strikes on the Islamic republic on Saturday, following 13 nights in a row hitting military targets there."We are talking to them," Mr Trump told reporters at the White House on Friday."I think they're being serious. I think … they are being by far the most serious that we've seen them, but that doesn't mean we get there."Asked what the exit strategy was for the Iran war, Mr Trump said there was a "military exit where we just keep going just the way we are, and we can even make it a heavier dose, and it's knocking out everything they have. Or there's a smarter strategy that you make a deal".He said Iran had a choice between making a deal or facing a "much higher level" of strikes after nearly two weeks of US attacks that left the ceasefire in tatters."We're locked and loaded. We're ready to go," Mr Trump said.He added that he did not know what the "tipping point" would be for a decision, but reiterated that Iran being close to developing a nuclear weapon would be a red line.Russia,China not arming Iran, Trump saysMr Trump also insisted that Russia and China were not arming Iran, despite reports both were feeding Tehran intelligence to target US forces."President Xi (Jinping) said he will not partake, and President (Vladimir) Putin said the same thing … I trust them," Mr Trump told reporters."I don't think they'd want to have me disappointed."Chinese Foreign Minister Wang Yi has met his Iranian counterpart Abbas Araghchi in Kyrgyzstan, calling for a memorandum of understanding aimed at easing tensions in the Middle East and the Gulf region, Chinese state news agency Xinhua reported.ABC/wires