Lithuanian diplomats have not confirmed the report.
"Two parliament members from Germany and Lithuania who planned to observe the elections were told they would be denied visa," the OSCE Parliamentary Assembly said, cited by AFP.
According to the French news agency, Neil Simon, spokesman for the OSCE Parliamentary Assembly, named the two banned observers as Marieluise Beck from Germany and Emanuelis Zingeris from Lithuania.
European lawmakers from international observer missions are denied visas in extremely rare cases, and the last time Minsk barred foreign observers was in 2006, Simon said.
The Lithuanian Ministry of Foreign Affairs said Lithuanian MPs were scheduled to go and pick their passports and visas on Thursday.
"According to information available to the Lithuanian Ministry of Foreign Affairs, Lithuanian parliamentarians who plan to go to observe elections in Belarus will go to the Belarusian Embassy to pick their passports with visas tomorrow. They have not received their passports yet. The Ministry of Foreign Affairs refrains from further comments regarding alleged issuance or denial of visas," Daiva Rimašauskaitė, spokeswoman for the ministry, told BNS.
Emanuelis Zingeris, chairman of the Lithuanian Seimas Committee on Foreign Affairs, confirmed on Wednesday Belarus had refused him a visa.
The politician, who planned to go to Belarus to observe the upcoming general elections on Sunday as part of the Organization for Security and Co-operation in Europe's mission, said it shows that the elections have "a preconceived direction."
"They have refused me entry. I have just been informed about the negative response, that I will not be issued a visa. It's a response not only for Lithuania but also for the international organization – the OSCE," Zingeris told BNS on Wednesday evening.
"It shows that our good wishes to have a closer look at the regime and see changes in the positive direction are in fact not fulfilling," Zingeris said.
Selective methods of visa issuance for election observers raises doubts over fulfillment of Belarus' international commitments and do not contribute to the possibilities for renewal of dialogue between Belarus and the European Union, Lithuania's Ministry of Foreign Affairs says, commenting on the denial of visa to Zingeris.
"The Ministry of Foreign Affairs is saddened by Belarus' decision to deny the Lithuanian representative, who planned to observe the Belarusian parliamentary elections as part of the OSCE Parliamentary Assembly's mission of short-term observers, a visa. Selective methods of visa issuance for election observers raise doubts over Belarus' openness to the OSCE values of free elections and democracy, fulfillment of Belarus' international commitments and do not contribute to the possibilities for renewal of dialogue between Belarus and the European Union," the ministry said in the statement.