A man alleged to have used social media to lure, abduct and rape a woman raised the prospect of group sex with her the day before, a court has heard.

The woman rejected the idea, but instead agreed to have sex with him.

The man, Randhir Singh, 21, and his alleged co-offender, Ajitpal Singh, 31, went on trial in the ACT Magistrates Court on Monday.

The pair are accused of sexually assaulting the woman in a car and at a unit in Belconnen in September last year.

They have pleaded not guilty to charges of abduction, committing acts of indecency, unlawful confinement, and rape.

A third man, Jaskaran Sandu, 33, allegedly involved fled the country to India shortly after the incident, the court heard on Monday.

The court heard Randhir Singh first chatted with the woman via chat application Tango on September 25.

They traded messages about sex and agreed to meet at Kippax Fair Shopping Centre the next day.

The court heard Randhir then asked her if she liked: "threesome sex".

She replied that she would answer when they met the next day and he wrote that it was good fun.

She then said "maybe next time" and that it depended on her "satisfaction" with the planned encounter.

The woman told him she wanted to take it "step-by-step".

The Crown – led by Margaret Jones – alleges she tried to abandon the meet when she saw Randhir at the mall with Ajitpal Singh and Sandu.

The court heard CCTV footage from the mall, yet to be played in court, would show Randhir chatting to the woman twice. 

Ajitpal Singh then allegedly threatened her child and said they would show her husband the Tango messages if she did not come with them.

The court heard Randhir grabbed her breast and forced her to give him oral sex in a car while they drove to Ajitpal's Belconnen flat.

He then allegedly unsuccessfully attempted to have sex with her in the apartment blocks carpark.

The Crown said the woman then begged to be let go, but Randhir ignored her pleas and had sex with her in flat's bedroom.

The court heard Sandu burst into the room during the sex and took two pictures of the woman on Ajitpal's phone.

Ajitpal then allegedly used the pictures to blackmail the woman into having sex with him.

Jurors heard a fourth man then took the woman home after hearing her crying and arguing with Sandu.

The trial before Justice Steven Rares continues on Tuesday.