Separate shootings in three US states of Maine, Illinois and Pennsylvania have left four people dead and at least ten others injured, reports say.

Two people were shot and killed early on Friday during a rampage across three northern Maine communities, authorities said.

The gunman, 35-year-old Anthony Lord, was a former convict that also injured three others before he was captured by officers.

58-year-old Kevin Tozier and 22-year-old Kyle Hewitt were shot dead. Two other men and a woman, whose names were not released, were injured.

Also, seven people were shot, one of whom fatally, in Chicago, Illinois on Friday, said Officer Veejay Zala, a Chicago Police Department spokesman.

Five men, aged between 19 and 23, were wounded in one shooting incident that took place about 5 pm near the 4400 block of West Maypole Avenue in the city's West Garfield Park neighborhood.

A man, 22, was fatally shot on the 2000 block of West Arthur Avenue in the city's West Ridge neighborhood about 1:40 pm. Also, a 19-year-old man was injured by gunfire in the city's Lawndale neighborhood earlier in the day.

In Overbrook, Philadelphia, which is the largest city of Pennsylvania, a person was shot dead and another was hurt outside the Tustin Recreation Center on Friday evening.

The gunfire, which took place around 7 pm, injured the second victim who was standing inside the center's playground.

Over 6,000 people have been killed and over 13,000 people have been injured by gun in the United States since January 1, 2015, according to the Gun Violence Archive.

About 4.5 million firearms are sold annually in the country at a cost of 2 to 3 billion dollars.