Police are appealing for witnesses after up to five men "indiscriminately" fired a weapon into a large crowd, injuring four people.
Gunshots were fired into a group of people at a communal BBQ in an open space in Clarence Gardens, near Regent's Park in north London just before 10.10pm on Saturday.
The injured include a 19-year-old woman; a 17-year-old woman; a 28-year-old man and a 73-year-old woman. Their conditions are not thought to be life-threatening.
The force said up to five unknown men had arrived at the BBQ and "indiscriminately discharged a firearm injuring four people".
Police including firearms officers and paramedics attended the scene.
Detective Superintendent Val John-Baptiste, of specialist crime North, said: "I need to hear from anyone who witnessed the incident or saw anything suspicious in and around Clarence Gardens, NW1.
"We thoroughly investigate every shooting in London, every incident and every weapon on our streets is of great concern to us.
"We know that Londoners feel exactly the same, and that's why it is vital that anyone with information shares with us what they know, either directly with police or anonymously via Crimestoppers."
No arrests have been made at this stage, the force said.
There is a cordon still in place on Clarence Gardens with an enhanced police presence in the area while the investigation is ongoing.