Both nations are part of the coalition that has been fighting the jihadists, which in recent months have been launching bloody assaults well beyond their traditional fiefdom in northern Nigeria.
Two female suicide bombers carried out the attacks in Kangaleri village, around 30 kilometres (19 miles) from the town of Mora in Cameroon, security and local sources said.
Nine people died when the first woman detonated a bomb in a tiny milk and donut restaurant. The second suicide bomber killed only herself, a local authority official said.
These blasts came as security sources bumped up the death toll to 41 in triple explosions Saturday in a Chadian city on Baga Sola on the shores of Lake Chad.
Another 48 people were wounded, the Chadian government said in a statement, after provisional figures by security sources late Saturday put the death toll at 37 with 52 wounded, some seriously.
The Chadian and the Cameroon armies have since the start of this year been involved in a regional offensive against Boko Haram, which has pledged allegiance to the Islamic State group operating in Syria and Iraq.
Boko Haram has waged a bloody insurgency since 2009 marked by mass abductions, village massacres and suicide bombings, sometimes by women and teenagers.
The attacks on Sunday are the 14th and 15th suicide attacks attributed to Boko Haram in far northern Cameroon since July, causing more than 100 deaths.
The powerful explosions in Chad struck at around 4:00 pm (1500 GMT) Saturday, with one blast targeting the fish market at Baga Sola and the other two occurring at a refugee camp on the outskirts of the city.
Humanitarian and security sources say several people blew themselves up in the middle of a crowd.
While climate change has reduced the lake's surface in recent years, it contains many islands and islets used by fishermen and its banks have dense vegetation, which makes infiltrations by Boko Haram Islamists much easier.
At least 17,000 people have been killed and more than 2.5 million made homeless since the Boko Haram insurgency began.
