SINGAPORE - Depressed after the failure of his relationship, an airline services assistant based at Changi Airport went into a female toilet there and took upskirt videos of women on different occasions.

Guo Jinquan, 27, had filmed three women, all air stewardesses, one of whom resembled his former girlfriend. But he was caught after a fourth woman, 29, discovered him and raised the alarm.

On Tuesday, Guo pleaded guilty to two of seven charges against him, with the other charges to be taken into consideration when he is sentenced in January.

These were for offences committed on Nov 30 last year and Jan 31 this year, comprising criminal trespass and insulting the modesty of his victims.

According to court papers, he had taken upskirt videos of his victims from under their cubicle doors. Minutes before being caught, Guo had recorded an unknown victim changing.

Referring to a report from the Institute of Mental Health, defence counsel Tang King Kai said his client has been diagnosed with schizophrenia and has had a "severe depressive episode".

A later report said Guo was hearing voices when he committed the offences.

Although the voices had not commanded him to do the acts, Guo was not in a normal state of mind at the time and had not acted rationally, the lawyer said.

Mr Tang said Guo should be spared jail as this would disrupt the treatment he has been seeking for his condition.

Deputy Public Prosecutor Ruth Teng disagreed, arguing that Guo would be able to receive treatment while in custody. She pointed out that the reports did not say Guo's condition had directly led him to offend.

He is expected to be sentenced on Jan 27, after District Judge Liew Thiam Leng called for further clarification on his mental state at the time of the offences.

The maximum penalty for criminal trespass is three months in jail and a $1,500 fine, while that for insulting the modesty of a woman is a one year jail term and a fine.