A murder investigation has been launched following the death of a 43-year-old man who was found with “serious lacerations” to his body.
Police were called to Westbourne Street, Stockton-on-Tees, at about 7.15am on Sunday, Cleveland Police said.
He was taken to hospital but later died, the force added.
Earlier in the day, at about 5.45am, officers attended an incident in nearby Yarm Road, where a 36-year-old man had suffered a head injury and also had lacerations to his torso.
He has since been released from hospital, and officers believe the two incidents are linked.
Police said two men, aged 18 and 39, have been arrested on suspicion of murder and attempted murder, while another two men, aged 20 and 29, have been arrested on suspicion of conspiring to cause grievous bodily harm with intent.
They are all currently in police custody.
Cleveland Police said in a statement: “Anyone who believes they have captured relevant CCTV or dashcam footage in the Westbourne Street/ Yarm Road areas at the time of the incidents are asked to contact police.
“Officers are also still appealing to anyone who may have witnessed either of the incidents or anyone with information to contact Cleveland Police on 101, quoting event number 232633.”