The Pakistani government is cracking down on slums in Islamabad because it fears the Christian population could overtake the Muslim majority.

A demonstration was held on Tuesday to condemn the Capital Development Authorities' (CDA) 2014 decision to eradicate a number of illegal slums, which are known as 'katchi abadis', in the capital.

There are 10 recognised slums in Islamabad, with a total population of around 120,000. According to AFP, the majority of people living in these areas are Christians and Afghan refugees. Local media reported that the CDA began to demolish illegal settlements on the outskirts of the city in the summer.

A CDA report said: "It is necessary to identify the fact that most of the katchi abadis are under the occupation of the Christian community who are shifted from Narowal, Sheikupura, Shakargarh, Sialkot, Kasur, Sahiwal and Faisalabad and occupied the Government land so boldly as if it has been allotted to them and it seems this pace of occupation of land may affect Muslim majority of the capital."

The removal of these slums is "very urgent to provide better environment to the citizen[s] of Islamabad and to protect the beauty of Islam," it added. "They look like ugly villages, whereas Islamabad was considered as one of the most beautiful cities of the world."

"Demographic problems" could result from too many Christians in Islamabad, the CDA claimed.

Activists are accusing officials of promoting sectarianism, and the rally on Tuesday was joined by leader of the opposition, Syed Kurshid Ahmed Shah, of the Pakistan Peoples Party (PPP).

Dawn.com reports that Shad said his party would "never support any action that renders the poor homeless". PPP Information Secretary Qamar Zaman Kaira said that it was vital that Pakistan welcomed all citizens, regardless of their faith.

"It is really condemnable" for the CDA to claim Pakistan "is only for Muslims", he added.

The Awami Workers Party has taken the issue to the Supreme Court, but the matter is yet to be resolved.

Persecution against Christians is a rising problem in Muslim-majority Pakistan. The US Commission for International Religious Freedom this year said Pakistan represented "one of the worst situations in the world for religious freedom" and recommended that the administration designated it a 'country of particular concern'.

In the State Department's International Religious Freedom Report for 2014 released in October, the Pakistani government was blamed for failing to "investigate, arrest, or prosecute those responsible for religious freedom abuses promoted an environment of impunity that fostered intolerance and acts of violence".

"Government policies did not afford equal protection to members of minority religious groups, and due to discriminatory legislation such as blasphemy laws...minorities often were afraid to profess freely their religious beliefs," the report said.