RIYADH: Explosions were heard in Riyadh early Saturday, AFP journalists reported, after Saudi authorities issued their first air raid alert in the capital since fighting returned to neighbouring Yemen.The Houthis have been fighting with Saudi-backed Yemeni government forces since the country's civil war reignited in July, when the group also declared a maritime blockade on Riyadh and began targeting its ships in the Red Sea.This is the first time the conflict has reached the capital, further shaking a global economy already rattled by nearly seven months of war between the United States and Iran."The area is under a hostile aerial threat," a message received shortly before 3:00 am (0000 GMT) by residents of the Saudi capital warned, urging them to stay indoors.AFP journalists then heard two explosions, before the alert was lifted about half an hour later by Saudi Arabia's civil defence agency.Saudi Arabia is yet to comment on the threat mentioned in the warnings sent overnight to residents of several regions and has not identified where it originated from.It comes after Riyadh accused the group of targeting Mecca on Wednesday, denouncing it as a "cowardly terrorist attack" on Islam's holy city, which welcomes millions of pilgrims each year, both Sunnis and Shias.The Houthis strongly denied the accusation calling it a "worn-out lie".In turn, the group reported dozens of retaliatory strikes carried out daily by Riyadh....