Suspected militants from Nigerian Islamist group Boko Haram have kidnapped dozens of people in raids in neighbouring Cameroon, officials say.

They said many of those kidnapped in the cross border attack against villages were children.

Four villagers who tried to fend off the attackers were killed, a security source has told the BBC.

Boko Haram has seized control of towns and villages in north-east Nigeria, and begun threatening neighbouring nations.

Chad, which also borders Nigeria, has just sent soldiers to help Cameroon in the fight against the jihadists.

The BBC's Randy Joe Sa'ah in Cameroon's capital, Yaounde, says this is the first time Cameroonian villagers have been kidnapped by suspected militants.

Previous kidnappings in Cameroon blamed on Boko Haram have been more targeted - with high-profile people or foreigners reportedly taken for ransom, he says.

'Burnt to ashes'

A security source told the BBC that it was the villages of Maki and Mada in the Tourou district near Mokolo city in Cameroon's Far North region, about 6km (four miles) from the Nigerian border, that came under attack.

Cameroon under pressure

The suspected militants arrived in the early hours of Sunday morning when it was still dark and left in the direction of Nigeria with scores of hostages.

Cameroon's Information Minister Issa Tchiroma Bakary confirmed the attacks saying between 30 and 50 people were taken in the raids - although he said an exact number was difficult to establish as investigations were ongoing.

"They burnt to ashes almost 80 houses," he said.

A police officer told the AFP news agency put the figure of hostages at around 60, saying "most were women and children".

Officials told Reuters that as many as 80 people had been kidnapped. Those abducted included about 30 adults and 50 children between the ages of 10 and 15, an army officer deployed to northern Cameroon told the agency.

Cameroon has criticised Nigeria for failing to do more to confront Boko Haram.

Analysis: Randy Joe Sa'ah, BBC Africa, Yaounde, Cameroon

There is a lot of anxiety in northern Cameroon because of the growing frequency of Boko Haram attacks - and growing number of those who take part in them. The military is also frustrated at not being able to chase the insurgents once they cross back into Nigeria.

Thousands of Cameroonian troops have been deployed to the north to stem the raids - which Boko Haram's leader warned in a video this month will increase in intensity. But Cameroon's border with Nigeria is long and porous, so it has been difficult to police.

News that Chadian troops are arriving to help patrol it has cheered residents. Tanks and armoured vehicles with Chadian soldiers have been seen arriving over the weekend. Chad's military has an impressive record of taking on insurgents - most recently in northern Mali.

Civilians now hope the countries will come to a deal allowing their armed forces to cross borders so that the militants can be contained.

The militants have kidnapped many people in north-eastern Nigeria, including more than 200 girls from a school in Chibok last April.

Those abductions caused worldwide outrage and sparked a social media campaign organised under the hashtag #BringBackOurGirls, calling on the authorities to do more to free the girls - who have still not been found or freed.

Sunday's kidnappings appear to be further evidence that Boko Haram is conducting a regional campaign of violence.

Last year, 27 people seized in Cameroon by suspected Boko Haram fighters were held for months before being freed in October. They included 10 Chinese workers and the wife of Cameroon's Vice-Prime Minister Amadou Ali.

It is not clear how their release was secured.

Several French hostages have also been kidnapped in Cameroon by Boko Haram and subsequently released.

France and Cameroon denied paying a large ransom for the release of the Moulin-Fournier family in 2013.

On Friday, Ghana's President John Mahama said African leaders would discuss plans this week to "deal permanently" with Boko Haram militants, and that a multinational force may be considered.

Boko Haram at a glance

• 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