The first man, 67, was found dead in an apartment on Ringvägen at 8.20pm. Police refused to go into details as to why they considered it a murder.
"When emergency services arrived on the scene, something wasn't quite right. I can't say more than that, unfortunately," Patrik Eriksson of the Stockholm police told the TT news agency.
The second man, 26, was found just after 10pm in a stairwell on Götgatan. He appeared to have died from heart complications, but once again Eriksson said that something felt amiss.
"It's not normal that a younger man dies just like that," he said.
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Officers, however, ruled out the theory on Monday morning, having found no connection between the two thus far. A coroner's report is expected to shed more light on the two cases within the next few days.