German Chancellor Angela Merkel said she was "dismayed" over the head-on collision of two commuter trains on Tuesday that killed at least nine people and injured more than 100.

"I am dismayed and saddened by the serious train accident this morning at Bad Aibling," Merkel said in a statement. "My sympathy goes out especially to the families of the nine people who have lost their lives.

"My thoughts are also with the many injured who are struggling with the consequences of the accident. I wish them a speedy and full recovery."

Merkel thanked the rescue services "for their tireless work... under difficult conditions" and said she was confident that the responsible authorities would "make every effort to clear up how this accident could happen".

READ: Number of German train crash victims increases, over 100 injured