Perry Kouroumblis, 65, was arrested at Rome airport and held for the alleged murders of Suzanne Armstrong and Susan Bartlett

• Get our breaking news email, free app or daily news podcast

The brother of a man accused of the 1977 Easey Street killings in Melbourne says he is “100% sure” that there has been a mistake and his brother is innocent of the double murder.

Perry Kouroumblis, 65, was arrested at Rome airport on Thursday Australian time and held for the murders of Suzanne Armstrong and Susan Bartlett. Police plan to apply to Italy for extradition for the man to face charges in Australia.

Sign up for Guardian Australia’s breaking news email