Lukashenka was due to have been sworn in on March 31, but postponed the ceremony for undisclosed reasons.
The Belarusian opposition claims the ballot was rigged, a charge supported by the European Union (EU) and the United States, which have imposed sanctions on Belarus.
According to the official results, 83 percent voted for Lukashenka and just 6.1 percent for his nearest rival, Alyaksandr Milinkevich, who has accused Lukashenka of an "unconstitutional grab for power."
Milinkevich, who is demanding new elections in which Lukashenka will not be allowed to stand, is currently visiting Vienna for talks with Austrian Chancellor Wolfgang Schuessel.
Austria currently holds the rotating EU presidency.
Milinkevich is hoping to use his trip to persuade the EU to put more pressure on the Lukashenka government.