Egyptian authorities have detained a Hamas leader upon arrival at the Cairo International Airport from Saudi Arabia, a security source said. Hassan Youssef al-Seifi, undersecretary of the Hamas-led Awqaf Ministry, arrived at the airport from Jeddah on Tuesday to attend a conference, the source said. "He was detained after his name appeared on a watch list," the source said. It was not immediately clear why he was detained. Relations between Egypt and Hamas have soured since the Egyptian military ousted democratically elected President Mohammed Morsi in a 2013 coup.