Armed police descended on a flat in Clapham and sealed off a road after two men scaled the roof of a building.
Locals reported a huge police presence in the south London street as officers attempted to detain the two men.
They are believed to have run out onto the roof after a warrant was executed for an arrest just after 7am on Saturday.
Armed units were deployed and a police helicopter was scrambled. The two men were detained and were brought down.
Following a search of the property, two firearms were discovered.
Police have not yet confirmed what the warrant was regarding to but the Standard understands it is not firearms-related.
A Met spokesman said that specialist firearms officers had attended as a precaution.
There were no shots fired and no reported injuries.
“Police executed a warrant at a residential address in Edgeley Lane, Clapham SW4 at around 7:02am on Saturday, 13 January,” he said.
“Two men are believed to have climbed onto the roof of the property. They have now been detained and officers are in the process of bringing them down. They will be taken to south London police stations.
“Colleagues from the National Police Air Service attended to provide support. Road closures have been put in place while the incident is dealt with.”