Foreign Minister Penny Wong has declined to say how many ISIS brides are currently in Australia, where they are living, or who was responsible for bringing them back.

At least two women and four children have returned to Australia after living in territory controlled by the Islamic State.

However, during a tense Senate Estimates hearing on Tuesday, Ms Wong and the Department of Prime Minister and Cabinet refused to provide further details.

Asked by Liberal Senator James Paterson whether Australians had the right to know the number of ISIS brides in the country, Ms Wong avoided giving any direct answer.

"We are aware about a cohort including Australian citizens seeking to return from Syria," Ms Wong told the committee.