The rebels had said the ceasefire didn't "concern" them as the deal was struck with Rwanda, not M23.
M23 rebels have continued fighting and advancing on one front of their offensive in the east of the Democratic Republic of Congo as a ceasefire came into force.
Clashes continued on Friday after the 1700 GMT deadline to cease fire near Bwiza, about 40 kilometres (25 miles) north of the provincial capital Goma, civilian and military sources said.
"M23 is at Bwiza," an administrative source said, adding that the rebels had taken over several villages in the area. AFP news agency was unable to independently confirm the account.
Fighting also took place during the day between the M23 and a Hutu militia in Bambo, 70 kilometres (45 miles) from Goma. "Heavy weapons fire can be heard, people are in a panic," a civil society representative said.
A security source confirmed the firing between the M23 and combatants from the Democratic Forces for the Liberation Rwanda (FDLR), a Hutu faction present in the DRC since the 1994 genocide of Tutsis in Rwanda.
Calm seemed to have returned to Bambo as evening fell.
DRC's President Felix Tshisekedi and Rwandan Foreign Minister Vincent Biruta met in Angola on Wednesday, agreeing to a deal on the cessation of hostilities in eastern DRC from Friday evening.
M23 rebels were to withdraw from "occupied zones", failing which the East African regional force would intervene.
But the rebels, a largely Congolese Tutsi militia, said on Thursday the ceasefire "doesn't really concern us", and called for "direct dialogue" with DRC's government.
"Normally when there is a ceasefire it is between the two warring sides," a spokesman for the rebels added.
Congo's government has ruled out negotiating with the M23, which it classifies as a terrorist group.
Then on Friday, M23 president Bertrand Bisimwa put out a statement in English saying, "Yet again, the M23 accepts the ceasefire as recommended" by the Luanda summit.
But he called on Kinshasa "to respect the said ceasefire, otherwise the M23 reserves itself the full right to defend itself".
The March 23 group had been dormant for years, but took up arms again late last year. The DRC accuses Rwanda of supporting the rebels, but Kigali denies the charges.