Robbers threatened to kick a heavily-pregnant woman in the stomach if she did not hand over her money and mobile phone.

The 29-year-old woman, whose baby is due this weekend (August 30-31), was approached by two men in Brasenose Lane, off Turl Street, Oxford. They pushed her against a wall and forced her to hand over the phone and a purse containing £26.

She was uninjured but left shaken and upset, and detectives have not yet been able to interview her.

Head of Oxford CID Det Insp Andy Bird said: "The birth of a child is a significant event in people's lives.

"These offenders have encroached upon that in a quite horrific way.

"I have not come across anyone making a threat against an unborn child before. This is unprecedented in terms of robberies in Oxford."

He said the incident was not being linked with other offences. The first robber was of mixed-race, about 25, and wore a hooded top and jeans. The other was white, aged 18 to 25, and also wore a hooded top.

The robbery happened at about 4.30pm on August 28.

Dc Sarah Wood, of Oxford police robbery team, said: "This is an horrific crime against a heavily-pregnant woman. They could see she was heavily-pregnant and one can only imagine the sort of person who would do this. They have to be seriously nasty people.

"This happened at a busy time and we are hoping someone would have seen these two on bikes.

"Our thoughts are with the woman and her husband. This should be a wonderful time for them and yet it has been ruined by cruel robbers who think of no-one but themselves."

The incident comes as robberies in Oxford are falling. Extra officers, including mounted police and traffic officers, have been drafted in this summer.

Anyone with information about the robbery should call Dc Wood on 08458 505505, or Crimestoppers free and anonymously on 0800 555111.