Islamist sect Boko Haram, whose attacks have killed hundreds in Nigeria, will continue its campaign until the country is ruled by sharia law, a senior member was quoted as saying by a British newspaper on Saturday.

"We will consider negotiation only when we have brought the government to their knees," Boko Haram spokesman Abu Qaqa told the Guardian.

"Once we see that things are being done according to the dictates of Allah, and our members are released (from prison), we will only put aside our arms - but we will not lay them down. You don't put down your arms in Islam, you only put them aside."

Boko Haram's attacks have become more sophisticated and deadly in recent weeks. A series of gun and bomb attacks killed 186 people in Nigeria's second city of Kano last Friday.

Gunmen suspected of being members of the group attacked a police sstation in Kano state on Friday, police and witnesses said, leading to more than an hour of running gunbattles.

Qaqa said the group's members were spiritual followers of al Qaeda, and said they had met senior figures in the network during visits to Saudia Arabia.

The Guardian said that for most of the interview Abu Qaqa used a modulator to disguise his voice, but local journalists confirmed that his undisguised voice matched recordings of previous interviews.

In an audio tape posted on the Internet on Thursday, the purported leader of Boko Haram, Abubakar Shekau, threatened to kill more security personnel and kidnap their families, and accused U.S. President Barack Obama of waging war on Islam.

Qaqa said recruits from neighbouring Chad, Cameroon and Niger had joined the group.

He said the rights of the country's 70 million Christians, half of Nigeria's population, "would be protected" under the group's envisioned Islamic state.

"Even the prophet Mohammed lived with non-Muslims and he gave them their dues," he said.

But he added that everyone must abide by sharia law: "There are no exceptions. Even if you are a Muslim and you don't abide by sharia, we will kill you. Even if you are my own father, we will kill you.

"People should understand that we are not saying we have to rule Nigeria, but we have been motivated by the stark injustice in the land. People underrate us but we have our sights set on (bringing sharia to) the whole world, not just Nigeria."