An Irish escort website encouraged men to pay for sex with Ukrainian women fleeing from Vladimir Putin's invasion, and live out their 'war inspired fantasies'.

A European anti-trafficking expert warned on Thursday that the Irish sex trade was already reacting to the refugee crisis which has seen an increase in demand from men trying to 'identify and have sex with' female evacuees.

Valiant Richey, a representative from the Organization for Security and Co-operation in Europe, gave the website as an example of the increased demand.

'We are already seeing the [sex work] market responding' to the refugee crisis, he said. 'For example, one of Ireland's largest escort websites offered men the opportunity to live out their 'war inspired fantasies' with Ukrainian women.'

Mr Richey said the same escort website had reported a 250 per cent increase in Ukrainian woman using it to advertise services since the war began.

The vast majority of people fleeing Ukraine since the invasion began on February 24 have been women. Under the country's martial law, men between the ages of 18 to 60 were required to stay and fight.

The existence of the website was revealed during a digital National Women's Council event on Thursday, during which Richey said there was a 'significant spike' in the use of online search terms that 'related to buying sex from Ukrainian women.' 

The anti-trafficking coordinator said some countries had seen a 600 per cent spike in such search terms, according to the.

'In other words, one of the early and measurable reactions in Europe to the crisis were attempts by men to identify and have sex with women and girls fleeing the conflict,' Richey said.

'The influx of vulnerable women and girls into Western Europe led to an immediate increase in interest by men in exploiting them.'

He said that the influx of evacuees coming from Ukraine, coupled with the increase in demand for men looking for Ukrainian sex workers, opened the door to sex traffickers who want to expose the crisis. 

Addressing the demand, he said, was the most effective way to combat trafficking.

'Since the start of the war there has been an immense spike in the demand, which will serve as a strong incentive for traffickers to recruit and exploit Ukrainian women at scale,' he told the event.

'Addressing demand today is the single greatest anti-trafficking tool we have, to prevent the current humanitarian crisis from becoming a trafficking one.'

Richey was joined by several other speakers at the event, that called on the Irish government to protect women and children fleeing the war.

Beyond Exploitation (Ireland's civil society campaign for equality and freedom from sexual exploitation) coordinator Mia de Faoite said doing so much be a top priority for the Irish Government as the war continues into its fourth month.

'This is a matter of urgency, women and girls are already disappearing into the hands of traffickers, many women have already been raped by soldiers or sexually exploited by buyers,' she said.

'We need all necessary safe-guarding measures to be put in place as a matter of urgency and those tasked with the responsibility of tackling the demand must be resourced and supported.'

In April, the United Nations warned that the evacuee crisis would increase the prevalence of sex trafficking, with traffickers taking advantage of the vulnerability of women desperately fleeing the country.

Human rights organisations have also warned of the risks posed by schemes in which citizens take fleeing Ukrainians into their homes.