Ahmad Sani Yerima oversaw the introduction of Sharia in Zamfara State
A Nigerian senator accused of marrying a 13-year-old Egyptian girl says he has done nothing wrong.
Ahmad Sani Yerima, 49, told the BBC that his fourth wife was not 13, but would not say how old she was.
He denied breaking the law but said he would not respect any law that contradicted his religious beliefs.
The Nigerian senate ordered an investigation after complaints from women's groups but the senator said he did not care what the groups thought.
A spokesman for the Egyptian embassy in Nigeria has said the girl is still at school in Egypt.
"Nobody has complained to the embassy in respect of the girl," Mohammed Saber told the AFP news agency.
He said however that the embassy "will follow the issue" because it is illegal in Egypt to marry an underage girl.
Mr Sani was the governor of Zamfara state, where he oversaw the introduction of Sharia law - for the first time in a northern state - in 1999.
He said he felt this was behind the uproar over his marriage.
"I consider all those complaining about this issue as detractors, because since 1999... many people have been waging different kind of wars against me," he told the BBC's Hausa Service by telephone from Egypt.
The senator said he had followed "standard rules for marriage in Islam".
"I don't care about the issue of age since I have not violated any rule as far as Islam is concerned," he said.
"History tells us that Prophet Muhammad did marry a young girl as well. Therefore I have not contravened any law. Even if she is 13, as it is being falsely peddled around.
"If I state the age, they will still use it to smear Islam," he said.
The BBC's Caroline Duffield in Lagos says newspaper reports of the marriage have created a storm among human rights groups.
Female senators - lawyers and doctors - who are protesting say that they fear for the child's health.
"What we are concerned with is that our minors, the girl child, should be allowed to mature, before going into marriage," Mma Wokocha, president of the Women's Medical Association and one of those behind a petition, told the BBC.
"This very evil act should not be seen to be perpetrated by one of our distinguished legislators... that is what we are saying.''
The senator is reported to have paid a dowry of $100,000 (£66,000) to the child's parents - and to have brought the girl into Nigeria from Egypt.
The women's groups want Mr Sani to be taken to court, to face a fine and a jail sentence.
They say he has contravened the Child Rights Act of 2003 which, although not ratified by all Nigeria's 36 states, is law in the capital, Abuja, where he lives and where his marriage is believed to have taken place.
"As a Muslim, as I always say, I consider God's law and that of his prophet above any other law," Mr Sani said.
"I will not respect any law that contradicts that and whoever wants to sanction me for that is free to do that."
Newspaper reports have also accused the senator of having previously married a 15-year-old girl in 2006.