Police say they have identified the perpetrator of a series of 2005 murders in Seoul's Yangcheon District, cracking a 20-year-old cold case.

At a press briefing on Friday, the Seoul Metropolitan Police Agency said investigators have officially named a man, who died in 2015 but was in his 60s at the time, as a suspect.

The case involves the death of a woman in her 20s and another of a woman in her 40s, five months apart, whose bodies were found with signs of strangulation and black plastic bags over their faces in a residential area of Yangcheon's Sinjeong-dong.

The cases were closed in 2013, but a team the Seoul police established three years later began looking into them again.

DNA evidence indicated that the same person had killed both victims.

The team expanded the search to deceased persons and identified the then-manager of a nearby building, who had previously been arrested in connection with a rape case.

Since the suspect had already died and been cremated, investigators had to visit 40 hospitals in the southern part of Gyeonggi Province, where he lived, to obtain his DNA sample.

The police plan to close the case with "no right to indict" since the suspect is dead.