Saudi Arabia is waiting for “serious steps” from Yemen’s Houthi rebels on a potential prisoner swap before responding to their offer of a ceasefire, an official told AFP on Tuesday. The Saudi-led coalition, which backs the government in Yemen’s conflict, is yet to comment on the surprise announcement from the Iran-backed Houthis, who called a three-day truce and dangled the possibility of a permanent end to hostilities. The rebels’ offer on Saturday, the seventh anniversary of the start of the war, came a day after a wave of cross-border drone and missile attacks on Saudi targets, including an…