"There is a decision from Cairo that any Syrian travelling to Egypt must apply for a visa at the Egyptian embassy," AFP quoted a staff member at the Egyptian consulate in Beirut as saying.
"A decision will be made some 10 to 15 days after the traveller has made his visa application," he said.
"I don't know whether this change is temporary or permanent. All I know is that it applies as of Monday," he added.
The United Nations says nearly 90,000 Syrians have registered with the High Commissioner for Refugees in Egypt.
But the actual number of Syrians who have sought refuge in Egypt is believed to be much higher, in part because the country did not require Syrians to have visas until this week.
Staff at Lebanon's Middle East Airlines (MEA) confirmed the change.
"Syrians now need a visa to go to Cairo. I have no information on the reasons behind the change," said a telephone operator.
MEA flights from Beirut to Cairo are frequently packed with passengers who have fled Syria by road into Lebanon, and then continue on by air to Egypt.
The confirmation of the new policy comes a day after several reports emerged of Syrians who were turned back on arrival in Cairo.
Egypt's state newspaper Al-Ahram reported Monday that passengers on a flight from the coastal Syrian city of Latakia were refused entry.
Egyptian media also reported Syrian passengers flying in on a Middle East Airlines flight were denied entry into Cairo.
Though he was eventually allowed into Cairo, prominent Syrian dissident Haytham al-Maleh waited for permission from the Egyptian authorities at the airport for two hours, he told AFP.
"I have connections, and I was able to secure permission to enter Cairo after two hours waiting in the airport," Maleh said.
"But I saw some 25 Syrian families being made to wait before deportation," he added.
"We are surprised by the decision, especially because it comes from Egypt, which is a sister nation to Syria," said Maleh, who is a member of the main Syrian opposition National Coalition and who is based in Cairo.
He said the Coalition is working to convince the Egyptian authorities to cancel the decision.
Egypt has seen unprecedented unrest since June 30, when massive demonstrations calling for President Mohamed Morsy to resign led the military to oust him.
Deadly street battles pitting pro and anti-Morsy youth have raged since in several Egyptian cities.
Reports emerged on Monday that Palestinians looking to return home to the Gaza Strip via Cairo were also being turned away by the authorities.