Both countries are part of a regional coalition that has been fighting the militants, who in recent months have extended their bloody assaults well beyond their traditional fiefdom in northern Nigeria.
Two female suicide bombers carried out the attacks in the Cameroonian village of Kangaleri, 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.
Several of the 29 injured were "very badly" hurt, added the official, who asked not to be identified.
The blasts came as security sources said the death toll had climbed to 41 in Saturday's triple explosions in the Chadian city of Baga Sola on the shores of Lake Chad.
Another 48 people were wounded, the Chadian government said in a statement.
One of the blasts targeted the fish market at Baga Sola while the other two occurred at a refugee camp on the outskirts of the city.
It was the first such attack on Baga Sola, and the belief that it was relatively safe had led tens of thousands of Nigerian refugees and Chadians displaced by Boko Haram violence to seek shelter there.
Humanitarian and security sources say several people blew themselves up in the middle of a crowd.
Call to surrender
Chad's far-north region has now suffered 15 suicide attacks attributed to Boko Haram since July, causing more than 100 deaths.
EU foreign policy chief Federica Mogherini on Sunday condemned the bloodshed as a "worrying attempt to destabilise the country".
Lake Chad is shared between Nigeria, Niger, Cameroon and Chad, all of which have since the start of this year been involved in the offensive against Boko Haram.
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 in 2009.
The group, which has pledged allegiance to the Islamic State jihadists operating in Syria and Iraq, has lost territory in the multi-national fightback but it has responded with guerrilla-style attacks and bombings.
The Nigerian army said Sunday it was closing in on Boko Haram fighters and urged them to surrender.
"They should follow their colleagues who have so far surrendered. Failure to surrender will result in serious consequences as our troops are fast closing up on them," army spokesman Colonel Sani Usman said in a statement.
The Nigerian military has claimed that more than 200 members of the militant group surrendered on September 25 when troops regained control of the northeastern town of Banki, a launching point for attacks into Cameroon.
There was no independent verification of the military's statement.
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