Cameroon has carried out its first air strikes against militant Islamist group Boko Haram, after it overran a military base and attacked five villages, officials have said.
The military repelled the coordinated attacks and regained control of the base, they added.
At least 41 militants and one soldier were killed, the officials said.
The Nigeria-based group is increasingly carrying out cross-border raids, threatening Cameroon's security.
The latest fighting was the most intense, lasting for three days along several fronts, reports the BBC's Jean-David Mihamle from Cameroon's capital Yaounde.
About 1,000 militants attacked five villages, including Amchide, and seized the nearby Achigachia military base, where they raised their black flag, army spokesman Lt Col Didier Badjeck told the BBC's Focus on Africa programme.
He said President Paul Biya then personally ordered the air force to intervene, forcing the militants out.
"Now the area is totally secured."
Lt Col Badjeck said the air strikes showed that Boko Haram would face a "hard reaction" if it attacked Cameroon again, with the government determined to use all its capability to protect its territory.
In a statement, Cameroon's Information Minister Issa Tchiroma Bakary said the multiple attacks showed that Boko Haram had adopted a new strategy aimed at "distracting Cameroonian troops on different fronts, making them more vulnerable in the face of the mobility and unpredictability of their attacks".
At least 34 militants were killed after the army raided one of their bases in Cameroon, while another seven were killed in a separate clash which also claimed the life of a soldier, Mr Bakary said, Reuters news agency reports.
Last week, Cameroon said it had dismantled a Boko Haram training camp on its territory, and had seized 84 children who were being trained there.
More than 40 of its soldiers have been killed in fighting with Boko Haram this year, according to Reuters.
Boko Haram launched its insurgency in north-eastern Nigeria in 2009, saying it wanted to overthrow the government and create an Islamic state.
It recruits mainly unemployed youth and has seized large swathes of territory in Borno state, raising fears that it could launch an assault on its main city, Maiduguri.
At least 2,000 civilians have been killed by the group in Nigeria this year.
The kidnapping of more than 200 schoolgirls by Boko Haram in April from the town of Chibok in Borno state sparked international outrage.
Who are Boko Haram?
- Founded in 2002
- Initially focused on opposing Western education - Boko Haram means "Western education is forbidden" in the Hausa language
- Launched military operations in 2009 to create Islamic state
- Thousands killed, mostly in north-eastern Nigeria - also attacked police and UN headquarters in capital, Abuja
- Some three million people affected
- Declared terrorist group by US in 2013