Skyrocketing use of illegal fireworks in the city is leading to injuries.

Two yahoos hurt themselves with errant pyrotechnics in separate incidents early Wednesday, police said.

Bronx cops responded to the first incident shortly before 1 a.m., on initial reports of shots fired on University Avenue.

Police later determined that an 18-year-old man had been struck in the chest while lighting off fireworks.

Wilson Doble was taken to Columbia Presbyterian Hospital, where he was listed in critical condition.

In the second incident, 33-year-old Wayne Jamieson was shooting off fireworks inside his Brooklyn apartment around 5 a.m. when one of the missiles backfired and hit him in the chest, police said.

He was taken to Kings County Hospital, where he is listed in critical condition, police said.

City officials reported a 4,000 percent surge in firecracker complaints during the first two weeks of this month, with 849 reports to 311 between June 1 and June 14 — up from just 21 over the same time span last year.