Oxford's bicycle thieves are being warned that someone will be watching them this summer.

For the first time, the city centre's CCTV cameras will be trained on cycle racks as part of the police campaign to cut bike thefts.

Officers will also be stopping cyclists in the streets if they are spotted jumping red lights, to check if they are the owner of the bike.

And every student at Oxford University has been told not to leave bikes unattended in the city centre over the summer. Police want to discourage the students from leaving cycles behind when they set off on their summer holidays, hoping that the bikes will still be there when they return in October.

In the past 12 months, about 1,800 bikes were stolen in Oxford, 454 of them in the city centre.

Pc Jim Abram, of Oxford police's auto crime unit, said: "Until the end of the summer, we're going to have a purge on cycle crime, using CCTV in the areas where there are bike racks. It's the first time we have done this."

All of the city centre's 42 CCTV cameras close to bike racks will have a default setting to monitor the rack. If CCTV operators spot a thief at work, they will call a joint team from the auto crime and city centre units for a rapid response.

Officers hope the initiative will catch more bike thieves in the act.

Pc Abram said: "When students go away for the summer, cycle crime goes down, because they're not aware their bike has been stolen.

"But when they return, it goes up, when they find their bikes are missing. We're trying to get in there first and stop that happening."

Between April 2006 and May this year, 1,805 bikes were stolen in Oxford. Thieves took 2,107 in the previous 12 months.

During the same period in 2004-5, 1,190 were stolen and in 2003-4, the figure was 2,060.

Two city centre Police Community Support Officers will be on patrol carrying cycle security-marking kits and can put postcodes on bikes on the spot if their owners agree.

Pc Abram added: "Don't leave your bike lying around for too long. But if you do have to, then make sure it is parked in a bike rack which is watched by the CCTV cameras.

"We take cycle crime seriously and anyone caught will be taken to court. If you steal a bike this summer, expect to see us."

David Jaques, of city cycling group Cyclox, said: "The CCTV generally already seems to be having an effect. I leave my bike at the station and it hasn't been interfered with or stolen for years.

"As for stop-checks, I would be happy to be stopped by a policeman if they were looking for stolen bikes."