In reference to the large rally turnouts for the RPF, Gayan said: "Crowds do not necessarily translate into votes."
Kagame told reporters the vote was "very democratic," and dismissed accusations of intimidation.
"The people of Rwanda were free to stand for election, those who wanted to, and to qualify, so I see no problem," he said after casting his vote. "Some sections of the media seem to be reading from a different page."
'Climate of fear'
Other rights groups and foreign diplomats have said that there has been pre-poll intimidation. Amnesty International, a rights group, said that the election would take place in a climate of fear.
Journalists have said that they have not been able to work freely, while one editor was shot and killed after stating that he had information about a dissident Rwandan general who was shot while in exile in South Africa.
RPF opponents have accused the ruling party of being involved in both cases.
Three candidates were not permitted to stand for the election and the authorities refused to register the opposition Unified Democratic Forces party.
Victoire Ingabire, the party's leader, has faced legal action since April after being accused of negating the genocide and abetting terrorism.
The Social Party faces similar problems and Bernard Ntaganda, its leader, has been behind bars since June 24.
Kagame has three challengers in the contest: Damascene Ntawukuliryayo, the deputy speaker of parliament, and head of the Social Democratic Party (PSD), Prosper Higiro, the senate vice-president and leader of the Liberal Party (PL), and Alvera Mukabaramba, chief of the Party of Peace and Concord.
Ntawukuliryayo is said to be the closest rival to Kagame, but other parties have said that the three are token opposition permitted to give the illusion of democracy - so-called "political satellites".
Ayo Johnson, political analyst with the London-based Viewpoint, told Al Jazeera that the opposition parties are justified in their criticisms.
"There has been a lot of intimidation - we have had violence. Clearly they are entitled to complain. Clearly Kagame is running Rwanda with an iron fist," he said.
"On the other hand you have economic reform and development which is moving very, very fast in that country.
"Kagame is convinced that he has a different form of democracy but that he should be judged on results."
Kagame has presided over economic growth and rebuilt institutions during his first term.
He has promised to transform Rwanda into a middle-income country in the next 10 years and the African hub for the IT industry.
Kagame won his initial seven-year presidential term in 2003 with 95 per cent of the vote. He was previously the leader of the minority-Tutsi military, which fought the majority-Hutus to end the 1994 genocide in Rwanda.
The genocide led to the deaths of about 800,000 people.