Seven people have been found shot dead in two houses in Illinois, US police say, and a manhunt for a suspected gunman is under way.

Police said they are seeking 23-year-old Romeo Nance in connection with the attack in the city of Joliet.

Joliet police chief Bill Evans said the suspect knew the victims, who were found in two homes across the street from each other on Monday afternoon. Police said Nance “should be regarded as armed and dangerous”.

Investigators in Joliet, Will County, said he was believed to be driving a red Toyota Camry. They urged anyone with information about the attack, 40 miles (64km) south-west of Chicago, to contact them. “This is an active investigation in which we are working with our area law enforcement partners,” Joliet police department said in a statement.

Chief Evans told a news briefing that police were notified at 12:04 local time (18:04 GMT) on Monday that several people had been found shot dead.

After arriving at the scene on West Acres Road, officers discovered seven bodies. Five were found in one house, and two in the other, Will County Sheriff’s deputy chief Dan Jungles said. “I’ve been a policeman 25 years. This is probably the worst crime scene I’ve ever been associated with,” Mr Jungles said.

The victims were reported to be members of the same family. The motive for the attack was not immediately clear.

Separately, authorities said they had been notified of two shootings a day earlier at different locations in Joliet. They said a car with the same number plate as the one linked to the discovery of the seven bodies on Monday was spotted in both locations.

One of the shootings resulted in the death of a 28-year-old man, who was shot in the head, authorities said. He was identified by police as Toyosi Bakare, who was originally from Nigeria and had been living in the US for the past three years.

Police said a 42-year-old man was shot in the leg at a separate location earlier that day, resulting in non-life threatening injuries.