Britain's military is scouting locations in the capital including residential buildings to station surface-to-air missiles during this summer's Olympic Games, the Ministry of Defence said on Saturday.
"Ground-based air defence systems could be deployed as part of a multi-layered air security plan for the Olympics, including fast jets and helicopters, which will protect the skies over London during the Games," a spokesman for the ministry said in a statement.
"Based on military advice we have identified a number of sites and... are talking to local authorities and relevant landowners to help minimise the impact of any temporary deployments," he said.
The ministry has made no final decision on deployment of missiles, but is evaluating sites alongside police, the statement added.
Britain is mounting its biggest peacetime security operation for the London Olympics, which start on July 27.
The statement was released after residents of an east London apartment block complained on Twitter of being told of a military and police deployment that might include missiles on top of their building.
Resident Brian Whelan, a journalist, told AFP he had been informed in a leaflet distributed Saturday by the gated private block's management company of plans to station 10 military personnel there for two months.
"They're going to do a dummy run and if it goes well, there will be high-velocity missiles stationed on my building, along with soldiers," he said.
"It seems like it's completely written in stone -- there's been no consultation. They announced it in a way that makes it seem like some kind of prize that I've won, to be living on an army base, which is insulting."
The building in Bow, east London was apparently selected because it has an old watch tower converted into a lift shaft and is a 10-minute walk from the Olympic site, he said.
A security force of more than 40,000, backed by a huge intelligence operation, will guard venues, athletes and the millions of visitors expected to throng the British capital for the Games.
"Lone wolf" terrorist attacks are a major concern for security forces but a range of other threats are also being considered.
In 2005, a day after London was named host city, four homegrown suicide bombers attacked three underground trains and a bus, killing 52 people.