* Robbers blast open bank vault with dynamite, loot cash
* Four banks, two police stations attacked
* Latest in string of security lapses in past few days
ONITSHA, Nigeria, Nov 27 (Reuters) - - Bank robbers armed with assault rifles and high explosives attacked four banks and two police stations in southern Nigeria, in a coordinated strike that left seven people dead, police said on Tuesday.
It was the latest in a spate of security lapses in Nigeria in the past two days, after a suicide bombing by suspected Islamists inside a military barracks on Sunday and a jail break in the capital Abuja in the early hours of Monday.
The attack took place late on Monday night in the remote town of Auchi, in Edo state. The robbers opened fire and detonated dynamite at several of the targets, police commissioner for Eddo state Hurti Mohammed told Reuters by telephone.
They robbed the vault in Access Bank but were unable to get money out of any of the other banks. Seven people, including a bus driver, were killed in the ensuing gun battle with police, he said, adding that the robbers had escaped.
"They shot sporadically and were able to gain access to the vault of one of the banks ... carting away an unspecified amount of cash," he said. "No policeman was killed."
The southern, Yoruba-dominated area where the attack took place was hundreds of miles away from the northern areas where Islamist insurgent group Boko Haram is violently challenging the authority of the President Goodluck Jonathan's government.
But Boko Haram have made forays into the south, including in Kogi state, which borders Edo to the north.
Mohammed rejected any link. Powerful, organised robbery and kidnapping rings operate across southern Nigeria.
"There is no relation between this incident and what is happening in the north," he said. "We suspect the attackers just to be robbers." (Reporting by Anamesere Igboeroteonwu; Additional reporting by Isaac Abrak; Writing by Tim Cocks; Editing by Jon Hemming)