An alleged Muslim plot to take control of schools is being probed by Birmingham, Agence France-Presse reported.

A leaked anonymous letter which outlined how to implement what it called Operation Trojan Horse emerged last year, raising concerns about how some of the 430 schools were being run.

At least 200 complaints will be examined, the city council said. A chief advisor was appointed to lead an investigation that has extended to 25 schools from an initial four.

A change of leadership at the four schools was hinted by the letter through an alleged plot. According to AFP, it provided instructions on ousting and replacing uncooperative head teachers and school governors.

"We have an obligation to our children to fulfill our roles and ensure these schools are run on Islamic principles," the letter stated. "We... are on our way to getting rid of more head teachers and taking over their schools."

The letter continued, "You must remember this is a 'jihad' and as such all means possible to win the war is acceptable."

Known to have a large Muslim population, Birmingham's 2011 census revealed some 22 percent of the city's residents to be Muslims.

"Since the letter emerged, whistleblowers including former staff have come forward, making claims that boys and girls were segregated in classrooms and assemblies, sex education was banned and non-Muslim staff were bullied," AFP reported. "In one case, it was alleged that the teachings of the firebrand Al-Qaeda-linked Muslim cleric Anwar al-Awlaki -- who was killed by a U.S. drone strike in Yemen in 2011 -- were praised in an assembly."

"As more schools have come forward than the ones named in the Trojan Horse document, issues have arisen about behavior in schools, the way in which schools are run," city council leader Albert Bore told BBC television.

"It is about, generally speaking, the behavior of the schools, what happens within the schools, the school day, the school assembly, the way in which children in schools are organized."

Known as academics, the allegations focus on a category of schools established from 2000 onwards. Even though the schools are state-funded, they are being controlled by self-governing councils.

Bore said it was "part of the frustration" that the city council had no remit in the schools, which answer to the national Department for Education.

"We do not know who's on the governing body (of the schools)," he said.

On a visit to Birmingham earlier this month, Prime Minister David Cameron spoke about the issue, saying, "We will not accept any school begin run by extremists or promoting extremist views."

The findings will be published by the council before mid-June, AFP reported.