Rwandan support for rebels in neighbouring Democratic Republic of Congo may be more widespread than previously believed, the BBC has found.
Kigali has already rejected UN accusations that it is backing the M23 rebel group which recently captured the strategic eastern city of Goma.
Two ex-rebel fighters told the BBC they were offered money from Rwanda to set up a new front further south.
More than 500,000 people have fled seven months of fighting in the east.
Rwanda has previously backed armed groups in eastern DR Congo as a way of fighting Hutu militias who fled there after Rwanda's 1994 genocide, in which some 800,000 people died.
The M23, who like Rwanda's leaders are mostly ethnic Tutsis, has also denied it is funded by Rwanda.
BBC East Africa correspondent Gabriel Gatehouse spoke to two former rebel fighters in Bukavu, which lies on the southern tip of Lake Kivu, some 200km (125 miles) from Goma.
They were from DR Congo's minority Tutsi ethnic group and said they had joined the rebel Congolese Movement for Change in July to fight for a better life for the people of the east.
They had spent several months in the bush fighting the army, thinking they were part of a home-grown movement.
"Then our chairman of this movement came with a delegation of the government of Rwanda, saying that the movement has been changed, we have to follow the instructions of the Rwanda government," Capt Okra Rudahirwa told the BBC.
He said he and his men were given monthly supplies of cash - sometimes as much as $20,000 (£12,500) dollars, with which they bought food, uniforms and medicines.
His commander, Col Besftriend Ndozi, told the BBC they were also put in contact with a senior M23 commander, a Col Manzi, who urged them to co-ordinate their efforts.
"Manzi told us that the Rwandan army had given him the authority to support us and to command us. He ordered us to continue our fight, just as M23 were doing in the north, so that together we would demoralise the government," Col Ndozi said.
The men said they decided to abandon the fight once they realised the scale of Rwandan involvement.
The Rwandan government has declined to comment on the allegations.
But many of the details of this account, including dates and names of intermediaries, tally with separate research carried out by the UN, our correspondent says.
A recent report by UN experts said the M23's de facto chain of command culminated with Rwanda's defence minister. Map
It also accused neighbouring Uganda of aiding the rebels.
Kampala has denied the allegations and has been mediating over the last week following the M23's capture of Goma.
Its military commander, Sultani Makenga, has said he will withdraw his forces to a 20km buffer zone around Goma in the coming days.
The group mutinied from the army in April, saying it was because a 2009 deal to end a previous uprising by a Tutsi militia had not been fulfilled.