A massive explosion has rocked a market in northeast Nigeria's Bauchi city, causing "heavy casualties" and setting the entire area ablaze with rescue workers struggling to reach the scene, the Red Cross said.

"There was an explosion in the market with a large number of women traders... at around 16:00 GMT," said Adamu Abubakar of the Red Cross on Monday. "There are heavy casualties of course, but for now we can't do anything until the fire is put out."

Earlier on Monday, another explosion had killed at least 20 people at a bus station in Gombe city in northeast Nigeria, the latest violence in the region repeatedly targeted by Boko Haram, the Red Cross said.

"There was an explosion at the Dukku motor park. The Red Cross mobilised with 20 body bags and they have all been exhausted. We are still looking for more bodies among the carnage," said Abubakar Yakubu Gome, the Red Cross secretary for Gombe state.

The bomb was planted near a bus that was parked and filling up with passengers, said Mato Yakubu of the National Orientation Agency, a government body responsible for the media.

He said the blast occurred at 09:50 GMT at the station on the outskirts of Gombe city.

Gombe shares a border with Borno and Yobe state, two of the areas hit hardest during Boko Haram's five-year uprising which has cost more than 13,000 lives.

No group has claimed responsibility yet for the attack, but Boko Haram has claimed a number of attacks at bus stations, often targeting people who are heading to Nigeria's mainly Christian south.

More than 1,500 people have been killed in Boko Haram attacks this year, according to Amnesty International.

AFP