Two youths were killed and as many as 16 other people injured early Monday in a shooting outside a Florida nightclub as parents were picking up their children from a "teen night" event.

Police in Fort Myers, Florida identified the dead as 14-year-old Sean Archilles and 18-year-old Ste'fan Strawder, who was described by local media as a star high school basketball player.

A "person of interest" has been detained and two other individuals were being held for questioning over the shooting at Club Blu, police said.

The motive was not immediately known, but police said in a statement "this incident was not an act of terror."

It came just six weeks after a gunman killed 49 people at a gay club in Orlando, Florida, the worst massacre on US soil since 9/11.

Gunfire erupted at around 12:30 am (0430 GMT) in the club parking lot as a "Swimsuit Glow Party" was breaking up, police, witnesses and the club said.

"As the club was closing and parents were picking their children up ... that's when all this happened," Club Blu said in a statement.

"We are deeply sorry for all involved. We tried to give the teens WHAT WE THOUGHT WAS A SAFE PLACE TO HAVE A GOOD TIME," it said, adding that there was armed security inside and outside the club.

Witnesses described people scattering at the sound of gunfire, ducking and running behind a nearby apartment building, with children as young as 13 reportedly among the injured.

"It was a young teen event. There were kids. The kid I was holding in my lap, he was 14 years old that got shot," Tatianna Nouhaioi, a neighbor, told ABC News.

"And then there was a little girl who also got shot and she was 13. One of the security guard's daughter got shot, so I mean there was kids 13, 14, 15, 16."

Police said "at least 14-16" people sustained minor to life-threatening wounds during the episode.

A nearby home and vehicles were also shot at, resulting in one minor injury, police said.

Television images of the scene showed one of the wounded being loaded into an ambulance while police with flashlights scoured the parking lot for evidence, marking where shell casings fell.

The area has been deemed safe, but multiple streets were closed.

Active scene

"The investigation is still very active as is the crime scene," a police statement said. "Investigators are working very hard to determine a motive and answer many of the questions you have submitted. However, at this time those questions will not and cannot be answered."

Earlier, police said they were searching for "other persons who may be involved in this incident."

An attack on a gay nightclub in Orlando, Florida on June 12 left 49 dead in the worst mass shooting in US history.

Police killed the gunman, Omar Mateen, a 29-year-old US citizen of Afghan origin, after a three-hour standoff.

The Islamic State jihadist group claimed responsibility for that attack, calling Mateen "one of the soldiers of the caliphate." US authorities have said he was apparently radicalized after watching jihadist propaganda online.

That rampage and other recent shootings have revived the fraught debate about gun laws in the United States.

President Barack Obama, a Democrat, has repeatedly called for Republicans in Congress to confront the cost of their opposition to gun control and spending on mental health and drug treatment.

"We refuse to fund drug treatment and mental health programs. We flood communities with so many guns that it is easier for a teenager to buy a Glock than get his hands on a computer or even a book," he said at a recent memorial service for five police officers shot in Dallas.

After the Orlando massacre, the White House denounced the "cowardice" of US lawmakers who failed to pass gun control legislation.

Last month, Democratic lawmakers staged a virtually unprecedented 24-hour sit-in in Congress after Republicans refused to allow a vote on two widely supported measures.