"The possibility of an act of terror is of course there as the reason for what happened," he said in an interview to Rossiyskaya Gazeta state newspaper, parts of which were published last night (local time).
Britain and the United States, as well as international investigators, suspect a bomb exploded on board of the A321 plane chartered by a Russian tourism firm, but Egyptian officials insist there is no evidence yet of an attack on the plane.
Russia has also kept from blaming the October 31 crash, which killed everyone on board, on terrorists, however President Vladimir Putin on Friday ordered a ban on all Egypt flights for the time being.
The Islamic State group's branch in the Sinai claimed responsibility after the crash and said it downed the plane in retaliation for Russian air strikes in Syria, but it has not said how.
The head of Airbus said no technical fault has yet been detected that might explain the plane crash.
"Well beyond the emotion and the compassion after this tragedy, I can say that so far, what we got from the investigation didn't trigger any action, technical action on our side, regarding the A-321 fleet," said Fabrice Bregier, the European manufacturer's chief executive officer.
"But we need to wait for the conclusion of the investigations," Bregier said at the Dubai Airshow.
Medvedev said about 80,000 Russians were vacationing in Egypt at the time when Putin ordered the halt, as Red Sea resorts are extremely popular among Russians during winter.
He said at a government meeting on Monday that "this security measure is necessary until the reason for the A321 crash is known."
Since Friday, about 25,000 Russian citizens have been returned from Sharm el-Sheikh, Hurghada and Cairo via special flights, with their luggage flown in separately, said Arkady Dvorkovich, a deputy premier.
Russia will need two more weeks to bring the remaining tourists back home, he told Medvedev at the meeting.