A firefighter was injured after arsonists struck twice within 20 minutes in the early hours of the morning.
The fireman suffered a broken nose while trying to put out a blaze at a lock-up garage in Chadwick Close, Crawley, on Saturday at 3.20am.
He was hit in the face by the garage door and had to be taken to hospital to have stitches.
A fire service spokesman said the officer was expected to be off work for a couple of weeks.
District Commander at Crawley Pete Martin said: "This was a deliberate fire and a needless incident.
"Firefighters' lives are put at risk and an arson where lives are endangered carries a life sentence so it's a very serious activity."
At 3am on Saturday another crew was called after a VW Golf, Mazda 323 and Fiat Punto were set alight in Green Lane, Northgate, Crawley.
Two of the cars were completely destroyed and the other was badly damaged.
Firefighters remained until 4.52am to secure the scene.
Both fires will be investigated by fire service teams and police.
A Sussex Police spokesman said it was not yet known whether they were connected.
l Investigation teams are also trying to establish the cause of another serious blaze which ripped through a town centre block of flats.
The three-storey property in Cavendish Place, Eastbourne was badly damaged by the fire on Saturday morning.
Flames could be seen billowing from the roof as firefighters tackled the blaze from three directions, with two hoses on the ground and one on a turntable ladder.
Fire crews were able to stop the flames spreading from the property, which was unoccupied. No one was injured.
The fire started shortly before 7am and was out by 9.33am. Crews stayed behind to dampen down the scene and investigate how it started.
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