More than 5,500 London firefighters have completed a second eight-hour strike in a dispute over new contracts.
Private contractors responded to 20 callouts, including eight fires, between 1000 and 1800 GMT on Monday, London Fire Brigade (LFB) said.
The Fire Brigades Union (FBU) said it called the walkout as staff faced the sack unless they agree to new rotas.
Two men were taken to hospital after being hit by vehicles on picket lines in Croydon and Southwark.
The first - thought to be a demonstrator in his 40s - was injured when he was hit by a car outside Croydon fire station at about 1520 GMT.
He was taken to hospital with pelvic injuries and the union's president, Mick Shaw, said the man had "rolled on to the bonnet, then rolled off" the vehicle.
A man in his 30s, thought to be the driver, was arrested.
At about 2100 GMT, FBU representative Ian Leahair was hit by a fire engine outside LFB's training centre on Southwark Bridge Road.
He needed hospital treatment for minor injuries and another man was arrested, police said.
LFB said "a significant number of protesters" had gathered outside the centre after the walkout ended.
The FBU said a third person was hurt near the centre on Southwark Bridge Road when a fire engine hit his hand.
'There are options'
Cover during the strike was supplied by private firm AssetCo, which signed a £9m seven-year deal with LFB last year.
It was using 27 fire engines and 170 contract workers.
LFB said protesters stopped fire engines entering some fire stations, but this did not affect the stand-in crews' handling of 999 calls.
An FBU spokeswoman said she was not aware of any such confrontations.
Originally the brigade wanted to end the current nine-hour days and 15-hour nights and bring in equal 12-hour day and night shifts.
LFB revised the offer to 11-hour day shifts and 13-hour night shifts, but this has been rejected by the union.
The dispute centres around the brigade asking firefighters to sign a new contract to bring the shift changes into effect.
The union said firefighters faced the sack if they did not agree to this.
Matthew Wrack, from the FBU, said: "There are options whereby we can compromise on the question of shifts, what we are not prepared to accept is the dictat that is being used in the current negotiations by London Fire Brigade management."
But London's Fire Commissioner, Ron Dobson, said: "Firefighters now need to ask their union representatives what this strike is really achieving, and why they cannot reach agreement with us on our revised offer of an 11-hour day and 13-hour night."
A spokesman for London mayor Boris Johnson said: "We are bitterly disappointed that a profession which prides itself on protecting and reassuring the public seem determined to torment Londoners over minor and extremely reasonable adjustments to their very flexible working arrangements."
And the fire minister, Bob Neill, said the FBU had "resorted to thuggish tactics".
"This sort of strong-armed intimidation solves nothing and just puts people's lives at risk," he added.
Firefighters also walked out for eight hours on 23 October.
The union and LFB are scheduled to meet on Tuesday for talks over a 47-hour strike planned to start on Friday, which is Bonfire Night and also the Hindu, Jain and Sikh festival of lights, Diwali.