A 26-year-old man has been seriously sexually assaulted by a group of men.
He was with another 25-year-old man in Greyfriars Road, Reading, when they got into an argument with eight or nine men at about 01:45 BST.
Police said the second victim was punched and a knife was brandished by the group.
The 26-year-old was then chased to Thames Path where he was seriously sexually assaulted.
A Thames Valley Police spokesman said it started when the victims spoke to two men outside the Metro Bank in Broad Street Mall.
Both were white and about 5ft 10ins tall. One was of medium build, in his 20s, and had a thin moustache. The other had very short hair and was wearing a grey tracksuit jumper with a hood.
The victims then walked together along West Street and onto Greyfriars Road, where they were stopped by the two men plus six to seven others.
An argument ensued between the victims and the gang, with one man brandishing a knife.
The 25-year-old victim was then punched by a mixed-race man while the 26-year-old was chased by four white men to Vastern Road where they demanded money.
They walked him to Caversham Road where he made several failed attempts to withdraw money from a cash point before running away and being chased to Thames Path.
Det Insp David Turton said: "These are two extremely serious offences which are being thoroughly investigated."