The M23 rebel group in eastern Democratic Republic of Congo has said it will stop fighting, following days of clashes with UN-backed forces.
M23 official Museveni Sendugo told the BBC its forces had already pulled back 5km (three miles) from the frontline.
Rebel leader Bertrand Bisimwa said the pull-back would allow an independent investigation into how shells fell over the border in Rwanda on Thursday.
Rwanda says the Congolese army fired the shells. Congo denies the claims.
The M23 is made up of deserters from the Congolese army. They are mostly ethnic Tutsis, like Rwanda’s leadership.
DR Congo and the UN accuse Rwanda of backing the M23, a charge it denies.
Their troops have been pounding rebel positions on the Congolese side of the border with Rwanda since last week.
As tension escalated on Thursday, UN Secretary General Ban Ki-moon appealed to Rwanda’s president for restraint.
Rwanda twice invaded its much larger neighbour during the 1990s, and the border area has been unstable for two decades.
Congolese government spokesman Lambert Mende told the BBC’s Newsday programme that M23 rebels were firing onto Rwandan territory “to give Rwanda a pretext for coming in openly in this war”.
A newspaper close to Rwanda’s government has published photographs showing a military build-up near the border with DR Congo.
The UN peacekeeping mission in DR Congo, Monusco, recently deployed a new 3,000-strong intervention brigade to tackle the rebels.
Rwandan Foreign Minister Louise Mushikiwabo said on Thursday that 13 “bombs and rockets” had been fired into Rwanda on Wednesday and 10 the following day.
This brought the number of attacks Congolese have carried out on Rwanda in the last month to 34, she said.
She accused DR Congo forces of targeting Rwandan civilians and said: “We have remained restrained for as long as we can but this provocation can no longer be tolerated.”
BBC Great Lakes service editor Ally Yusuf Mugenzi says that even when Rwanda invaded Congolese territory, it never made such strong accusations against the Congolese army.
Congolese army spokesman Col Olivier Hamuli told the BBC that his forces would never fire at civilian populations.
“That could only be rebels,” he said, adding that M23 fighters, and not soldiers, were in the area from which the shells were fired.
This was backed up by Mr Ban’s assistant, Edmond Mulet, who told the UN Security Council that UN forces in the DR Congo had witnessed M23 rebels firing artillery into Rwanda but not the Congolese army, diplomats said.
Mr Mulet ended the session by informing members that Mr Ban had telephoned Rwandan President Paul Kagame to urge restraint.
At least 800,000 people have fled their homes in DR Congo since the M23 launched its rebellion in April 2012.
The M23 rebel movement is named after a 23 March 2009 peace deal that ended four years of rebellion in eastern Congo.
The rebels complained the Congolese government had failed to honour the agreement, which included integrating them into the army.
Eastern DR Congo has been wracked by conflict since 1994, when Hutu militias fled across the border from Rwanda after carrying out a genocide against Tutsis and moderate Hutus.