Suspected Boho Haram militants have reportedly killed 145 people in two attacks on villages near Lake Chad in northeastern Nigeria.

On Wednesday night the Islamist militants entered the village of Kukawa and gunned down 97 people at mosques and in their homes, eyewitnesses report.

The previous day they stormed two villages near the town of Monguno and killed 48 people just as they were finishing evening prayers.

Babami Alhaji Kolo, who witnessed Wednesday's attack and fled to the city of Maiduguri, told AFP news agency that more than 50 militants had been involved.

"The terrorists first descended on Muslim worshippers in various mosques who were observing the Maghrib prayer shortly after breaking their fast," he said.

"They... opened fire on the worshippers who were mostly men and young children.

"They spared nobody. In fact, while some of the terrorists waited and set most of the corpses on fire, others proceeded to houses and shot indiscriminately at women who were preparing food," he said.

There has been no official confirmation of the death toll, however an anonymous military source told the news agency that the Nigerian military had "responded with aerial bombardments on terrorist positions".

On Tuesday night the militants launched an attack on a mosque, then proceeded into the villages and set the houses on fire, a Monguno resident told BBC Hausa.

Describing the events at one of the villages attacked, he said: "They were praying in the mosque when Boko Haram attackers descended on the village. They waited till they finished the prayers. They gathered them in one place, separated men from women and opened fire on them.

"Many died, some escaped. They then set the village on fire. I saw five victims with bullet wounds who managed to escape. They were brought to [Monguno] on wheelbarrows, before they were transferred to vehicles that took them to hospitals."

These are thought to be the worst Boko Haram attacks for a number of weeks, although AFP estimates that 400 people have been killed by the group since President Muhammadu Buhari came to power at the end of May. Promising to defeat the extremists and secure the northeast of the country was a key part of his presidential campaign.

In total, the militants are believed to have killed at least 15,000 people since 2009.