Gunmen have killed 135 civilians in north east Nigeria since Wednesday, a senior official from the region has told the BBC.

Borno state senator Ahmed Zannah said the killings took place in at least three separate attacks in the state.

The attackers are suspected to be from the Islamist Boko Haram movement.

At least 1,500 people, half of them civilian, have been killed in the restive north-eastern region this year, according to Amnesty International.

The organisation blamed both "an increase in attacks by Boko Haram and uncontrolled reprisals by Nigeria's security forces" for the high death toll.

Women 'abducted'

Senator Zannah said the attackers first target was a teacher training college in the town of Dikwa.

They killed five people there and abducted several women, he said.

The attackers burned down the college library before escaping, Mr Zannah said.

The militants then attacked two villages near the border with Cameroon killing a further 130 people, the senator said.

The attacks took place on Wednesday and Thursday, with initial reports claiming around 70 people had been killed.

The Nigerian military has not yet commented on the attacks.

A state of emergency has been in place since last year in the states of Borno, Yobe and Adamawa in north-east Nigeria.

Human rights groups have criticised both Boko Haram and Nigeria's military for failing to protect civilians.

Amnesty International said last month that Nigeria's army killed around 600 people after a Boko Haram attack.

Some 250,000 people have been forced to leave their homes because of the fighting, the Nigerian government's relief agency said.

Boko Haram has waged an insurgency since 2009 to create a strict Islamic state in northern Nigeria.