OUAGADOUGOU (Reuters) - Unidentified assailants killed at least 43 people in raids on villages in northern Burkina Faso on Sunday, in one of the deadliest such attacks of the past year, the government said.

The attackers struck at least two villages inhabited by Fulani herders in the North region, near the border with Mali, the government said in a statement on Monday.

No claim was immediately made for the attack, but tit-for-tat reprisal killings between the Fulani and rival farming communities have surged over the past year across Burkina Faso, Mali and Niger, compounding violence by jihadist groups with links to al Qaeda and Islamic State.

The violence killed hundreds of civilians last year across the Sahel, a semi-arid strip of land beneath the Sahara Desert, alarming Western powers who have poured money and troops to combat the Islamist groups. It comes as the United States considers a drawdown of troops in the region.

Corinne Dufka, West Africa director for New York-based Human Rights Watch, said Sunday’s attack was one of six incidents in northern Burkina Faso since the start of the year that the organization is investigating in which vigilante fighters allegedly killed civilians or suspected jihadists.

A government spokesman did not immediately respond to a request for comment.

President Roch Marc Kabore signed a law earlier this year providing support to local vigilantes, including two weeks of military training, unspecified equipment, healthcare and bonus payments.

Even before the law was adopted, there were an estimated 40,000 vigilante groups called koglweogo - “guardians of the bush” in the Moore language - that have sprouted up in response to instability across the country.

Some of them have faced allegations they massacred civilians - charges they deny.

Jihadists, many transplants from neighboring Mali, have repeatedly stoked ethnic conflict by closely associating themselves with the Fulani, causing Fulani civilians to bear the brunt of reprisals by soldiers and vigilantes.

Last year was Burkina Faso’s deadliest in recent memory, and the violence has continued unabated this year. Two attacks in northern Burkina Faso in January killed 36 and 39 people, respectively, and gunmen killed 24 people in an attack on a church in February.

The violence has forced more than half a million from their homes and made much of the north ungovernable.