A snooker ball was thrown through the window of a Brighton bus, flinging broken glass into a student's eye.

The attack was the fourth of its kind this week and bus chiefs today asked: "What are these people trying to do - kill someone?"

The number 25 service was travelling north in Lewes Road, at Wild Park, when the ball was hurled across the street.

It shattered a side window, showering a Sussex University student in his 20s.

Blood poured from a wound and he was treated at the scene by paramedics, then taken to the Royal Sussex County Hospital, Brighton.

It was not known today how serious the injury was.

Vandals hurled bricks at three buses on Wednesday, shattering windows and sending slivers of glass over a driver.

Two attacks were carried out on the same bus.

Its windscreen was replaced in the morning after the first attack and the new window was smashed a few hours later.

The attacks happened in Sackville Road, Hove, Carden Avenue, Brighton and Beaconsfield Villas, Brighton.

Police are studying CCTV footage from bus cameras to trace the culprits. Roger French, managing director of the Brighton and Hove Bus and Coach Company, described the attacks as despicable.

He said: "The problem is very serious. The injury to the student is bad enough, but the ball just missed the driver. It doesn't bear thinking about what might have happened had it hit him and the bus had gone out of control.

"What are these people trying to do - kill someone? This must stop."

Police are appealing for witnesses and anyone with information should contact Brighton police on 0845 6070999.