Rwandan President Paul Kagame has never made any secret of what he thinks of Burundian president Pierre Nkurunziza's controversial third term. "How can one say 'I'll stay whether you like it or not'? That's a big problem," he tweeted on May 8. Those remarks were made before Nkurunziza had officially entered the race as a presidential candidate.

Nkurunziza was sworn in once again as president of Burundi last week, and tensions with neighboring Rwanda are rising. 30 Rwandans are reported to have been detained in Burundi over the last few days. The reason for their detention remains unclear. Rwanda has lodged an official protest with Burundi, demanding an explanation and the release of its citizens.

Burundi suspects coup plotters in Rwanda

This diplomatic spat follows months of deepening mutual mistrust between the two small East African neighbors. Suspicions in Burundi that Rwanda was backing opponents of President Nkurunziza came to a head after the failed coup in May.

"We know that some of the coup plotters are now living in Rwanda, at least three of them," Burundi's foreign minister Alain Nyamitwe told the New York Times at the end of July. There was evidence that Rwanda was "not helpful" in this matter,he said.

Burundi has also applied to Rwanda for the extradition of suspects linked to the murder of security chief Adolphe Nshimirimana, a close aide of Nkurunziza, who was responsible for the police crackdown on opponents of his regime.

With Nshimirimana's assassination, Burundi's crisis took yet another turn for the worse. But is there any substance to allegations leveled against Rwanda by Burundi? Gesine Ames from the Ecumenical Network Central Africa - a Berlin-based association of faith-based and civil society groups in the Great Lakes region - said "they are bit far-fetched, there is no clear evidence as yet."

There are some 72,000 Burundian refugees in Rwanda and they include opposition figures and journalists critical of the Burundian regime. "But you cannot conclude from this that Rwanda harbors or tolerates political conspirators," Ames said.

Rwanda suspects FDLR rebels in Burundi

Rwanda denies all involvement in the abortive Burundian coup and in turn accuses Burundi of backing FDLR Hutu rebels. The FDLR, or Forces Democratiques de Liberation du Rwanda, (Democratic Forces for the Liberation of Rwanda) has among its ranks suspected members of the Interahamwe, which carried out the Rwandan genocide in 1994.

The FDLR is active in the east of the Democratic Republic of Congo (DRC) and is still perceived by Rwanda as a threat. In the past, this has been sufficient grounds for Rwanda to periodically send troops into the DRC. Meanwhile rumors have been circulating in Rwanda over the last few weeks that FDLR rebels were now on Burundian soil near the Rwandan border. However, such accounts have not been verified.

Could the tensions between Rwanda and Burundi lead to open conflict between the two nations? Filip Reytjens, a political scientist specializing in the Great Lakes region at the University of Antwerp in Belgium, told DW he thinks "Kagame wants to see Nkurunuziza overturned, but the question is how far he will go to achieve that?"

Reytjens believes Kagame will end up seeking some sort of working arrangement with Nkurunuziza and that the situation will stabilize in the coming weeks and months, barring another attempted coup or assassination.

Regional conflict

"I believe both countries - drawing on past experience - will do everything to avoid armed conflict," said Ames. Burundi - and not just Rwanda - was scarred by ethnic conflict between Hutus and Tutsis in the 1990s. Both countries are still traumatized.

Nonetheless the potential for conflict should not be underestimated. "We are concerned by the rift opening up in the region and this conflict is a sign of that," Ames said. The worry is that the region will split up into two rival blocs with Tanzania, Burundi and Kenya on one side and Rwanda and Uganda on the other.

Relations between Rwanda and Tanzania are at a low ebb.

This is because Dodoma accuses Kigali of being responsible for the bloodshed in eastern DRC in which M23 rebels were pitted against UN and DRC government troops.

Rwanda is widely regarded as having financially backed and trained the M23 forces which have since been disbanded.

In the Burundian crisis, Tanzania took sides against Rwanda and supported the re-election of Nkurunziza. This helps to explain why mediation efforts by the East African Community (EAC) petered out. "More diplomacy, negotiations and determination" would have been needed for them to succeed, Ames said. She also appealed to international donors - such as the European Union - to force the states in the Great Lakes region to work together with one another. Otherwise other conflicts may break out.