YOLA, Nigeria (Reuters) - A bomb at a camp for people who have fled Boko Haram and a suicide attack on a bus station killed at least 12 people in northeast Nigeria on Friday, officials said.

There was no immediate claim of responsibility for the bombings. About 2.1 million people have been displaced and thousands killed in a six-year-old campaign by the jihadist group to carve out an Islamist state.

The group has killed around 800 people in bombings and shootings since President Muhammadu Buhari took office in May, vowing to crush the militant Islamists.

One bomb was at a camp for internally displaced persons (IDPs) at a school in a hamlet on the outskirts of the Adamawa state capital, Yola.

"So far seven persons lost their lives and 20 persons were injured in the bomb blast that occurred in Malkohi Internally Displaced Persons camp," said Sani Datti, a spokesman for the National Emergency Management Agency (NEMA).

It was the first bomb attack on such a target in the conflict. Most IDPs are living in government-run camps, with host families or with religious organisations in the city of Maiduguri in Borno state, the heartland of the insurgency.

A‎damawa state hosted over 250,000 people earlier this year and has received many women and children freed by troops from Boko Haram camps, as well as thousands of Nigerian refugees who fled to Cameroon and have since been evicted.

"Among the injured, seven were treated and discharged while 13 persons including four NEMA officials are still receiving treatment," added Datti.

He said the bomb had been planted in a tent and went off at around 10:50am (0950 GMT).

Alhaji Haruna Furo, of Adamawa state Emergency Management Agency, said five people were killed when a female suicide bomber detonated a device in a bus station in the town of Madagali at around the same time.

Madagali is in the northernmost part of Adamawa state, which borders Cameroon and Borno state.

Boko Haram controlled the area for months in 2014, but were pushed out in March as part of a drive by troops from Nigeria, Niger and Chad to reclaim territory from the insurgents.

Now dispersed Boko Haram fighters frequently launch attacks on places of worship, markets and checkpoints.