Rwanda's Green Party, the country's tiny but main opposition, said on Thursday it was challenging moves to change the constitution to allow strongman and President Paul Kagame to stand for a third consecutive term in elections in 2017.
"We submitted a lawsuit to the Supreme Court yesterday, demanding the court block parliament from any future plans to reform the constitution, especially article 101 about the lifting of presidential term limit," party president Frank Habineza told AFP.
The Rwandan constitution, adopted in 2003, limits the number of presidential terms to two, and therefore bars Kagame — elected first in 2003 and again in 2010 — to stand for a third term.
But officials last week said parliament will over the next two months debate a change in the constitution in response to what Kagame's aides have described a "popular demand".
According to parliament speaker Donatilla Mukabalisa, petitions signed by a total of two million people — or roughly 17 per cent of the population — have demanded that Kagame be allowed to stay in office.
Habineza said the challenge centred around the Green Party's belief that the constitution can only be revised "to only reduce or prolong the duration of the president's mandate."
Reacting on Twitter, Kagame said: "They are exercising their right… The Green Party, good thing!"
Kagame, 57, has been at the top of Rwandan politics since 1994, when an offensive by his ethnic Tutsi rebel force, the Rwandan Patriotic Front (RPF), put an end to a genocide by Hutu extremists that left an estimated 800,000 members of his community dead.
He first served as defence minister and vice president, and then took the presidency by winning 95 per cent of the vote. He was re-elected with a similarly resounding mandate.
Rwandan officials have strongly denied that it is Kagame who is seeking a third term, insisting that the president — hailed by his supporters as a guarantor of post-genocide security and stability, as well as a champion of economic development — enjoys popular support for him to stay.
The announcement comes amid a wider controversy in Africa over efforts by leaders to change constitutions in order to stay in office.
Last year Burkina Faso's former president Blaise Compaore was chased out after trying to extend his stay in power, while Rwanda's southern neighbour, Burundi, has been gripped by weeks of civil unrest and experienced a coup attempt over President Pierre Nkurunziza's attempt to do the same.