The United Democratic Forces, the Democratic Green Party of Rwanda and the Social Party Imberakuri said that was the only way to ensure peace in the central African country.
"We urgently call for urgent direct talks between the ruling bloc and the genuine opposition parties for a transitional government of national unity involving all stakeholders which will organise free and fair elections.”
"We believe that this will be the only solution to achieve sustainable peace in Rwanda," they said in statement.
Kagame won 93 percent of the vote in the August 9 presidential polls for which his government was criticised of excluding the real opposition.
Of the three parties, only the Social Party is registered. Its founding leader, Bernard Ntaganda, who had wanted to challenge Kagame has been in detention since June on charges of denying the 1994 genocide.
United Forces Democratic party leader Victoire Ingabire also faces similar accusations and her movement outside Kigali is restricted, while the Green Party's deputy chief Andre Kagwa Rwisereka was murdered in July.
The groups also called for Ingabire and Ntanganda to be freed as well as for an international independent probe on Rwisereka's death.