Video seen by Reuters showed vehicles ablaze and thick black smoke billowing across a wide stretch of road.
The accident happened on a motorway that connects Lagos and the city of Ibadan, Lagos State Emergency Management Agency (LASEMA) spokesman Adeshina Tiamiyu said. He said a distress call was received at around 05:33 p.m. (1633 GMT).
“Nine people are dead and four injured are in hospital”, said Tiamiyu.
A spokesman for the Federal Road Safety Commission, Bisi Kazeem, said the crash happened around Otedola bridge on the section of the road heading out of Lagos.
He said the cause of the accident was brake failure. He added that the tanker, five buses, two trucks, a tricycle and 45 cars were burnt out.
“As a government, we would not relent in putting measures in place to ensure safety of lives and property of all residents,” said Lagos state government spokesman Kehinde Bamigbetan in an emailed statement.
“We extend our deepest commiseration to the families of persons who lost their lives as well as properties to the incident.” The statement added that the state government was clearing damaged vehicles from the road.
(Editing by Chijioke Ohuocha and Andrew Roche)