A Muslim couple have been denied Swiss citizenship after they refused to shake hands with people of the opposite sex during their interview, the BBC reported.

Officials said the decision was taken because of the couple's failure to integrate and respect gender equality.

The couple, interviewed months ago, also struggled to answer questions by members of the opposite sex. 

The Swiss authorities said aspiring citizens must be well integrated into the Swiss community and demonstrate an attachment to Switzerland, its institutions and a respect for the Swiss legal order.

The couple, from North Africa, previously failed to meet citizenship criteria when they applied in the city of Lausanne.

The mayor of Lausanne, Gregoire Junod, told AFP that freedom of religion was enshrined in local laws but "religious practice does not fall outside the law."

In 2016 a northern Swiss canton had also ruled that parents or guardians of students who refuse to shake a teacher's hand could now face fines of up to 5,000 Swiss francs (S$6,955).

'Religious belief is no excuse for refusing to shake a teacher's hand,' regional authorities ruled Wednesday, reversing one school's controversial decision to grant exemptions for Muslim students wary of touching the opposite sex.

The decision came after a national uproar over revelations that a school allowed two brothers, aged 14 and 15, not to shake their teachers' hands after they complained that doing so was counter to their religious beliefs if the teacher was a woman.