Three teenagers have admitted harassing and threatening two women who a judge said had caught their attention on a late-night bus because they were a same-sex couple.

But the two victims – Christine Hannigan and Melania Ramirez, whose surname was Geymonat at the time – will have to give evidence in court on Friday after one of the accused denied that his actions were motivated by hostility based on the women’s sexual orientation.

Highbury youth court was shown CCTV footage of the incident, which occurred on the top deck of a bus in Camden in the early hours of 30 May.

After Hannigan and Ramirez ascended the steps and took up seats at the front of the bus, the teenagers were seen quickly moving from the back and taking up positions near the women, in what the judge said was “like the tide washing in”.

Over the course of nine minutes, the incident escalated into a scuffle before the youths got off and the women were left bloodied and without belongings including a mobile phone. Both were taken to hospital for treatment to facial injuries.

The teenagers, aged 15, 16 and 17, appeared in court on Thursday after denying charges of harassment by using threatening or abusive words or behaviour. The prosecution insists the women’s sexual orientation was an aggravating factor.

After viewing the footage, the judge, Susan Williams, said: “I don’t think I would describe it as a ‘hate crime’, in inverted commas, but they quite clearly targeted this couple and moved towards them.”

Play Video 0:42 Police release CCTV footage of attack on two women on London night bus – video

She added: “I think it will be a hair-splitting exercise but it’s perfectly obvious that this was a same-sex couple that has provoked their interest and the interaction between them. The offence cannot be explained in any other way. I do regard this as an aggravating feature and it would be reflected in the sentence.”

Saira Khan, prosecuting, said a “scissoring gesture” made by one of the youths towards the women would be regarded as an insult targeted at their community. Immediately after this gesture, coins were thrown at the women, who she said had told of facing demands to kiss and “provide entertainment”.

The prosecution’s case was contested by David Wood, a solicitor for the 17-year-old who had thrown coins and made what the prosecution described as a “kissing gesture”.

“The coin-throwing is pathetic. It’s a criminal offence, but it has nothing whatsoever to do with an attack based on hostility with regards to sexual orientation,” said Wood, who insisted he wanted to avoid a scenario where he would have to cross-examine either Hannigan or Ramirez.

The two women were in the building on Thursday but not in the courtroom and have agreed to attend on Friday in order to give evidence. The 17-year-old will also give evidence.

Wood said it was “quite clear that the teenagers were attracted by two older females paying attention to each other and being affectionate, which they [the women] had every right to”, but he rejected the claim that his client’s coin-throwing was a case of public disorder based on hostility to the pair because of their sexual orientation.

Addressing the 17-year-old at the end of the hearing, Williams said: “You say you were not being hostile to these ladies on the basis of their sexual orientation. That is an issue that has be resolved because it does make the case more serious if the court comes to the decision that this was what was going on at the time and it does mark it as more serious.”

The 16-year-old, from Wandsworth, pleaded guilty to the theft of Hannigan’s handbag and handling stolen goods relating to her £300 mobile phone. He will be sentenced on 19 December at Wimbledon youth court.

The 15-year-old, from Kensington and Chelsea, admitted handling Ramirez’s stolen bank card and will be sentenced on 23 December.

Charges were dropped on Thursday against another 17-year-old, who was allowed to leave court.

After they became the focus of global sympathy and outrage when an image of them sitting bloodied and in shock on the bus went viral, Ramirez and Hannigan told the Guardian in June that they were determined to see that something positive came from their experience.