What is this symbol? I keep seeing it and I assume it's religious?

The Arabic letter "nun" (with a cross replacing the dot) an abbreviation for the Arabic word for Christian, painted on the homes of Christians by Islamic extremists who demand that they convert. Western Christians can show solidarity with Christians who are being persecuted in the Arab world by Islamic extremists.

It could be the symbol for Chrislam,but I'm not entirely sure.

Arabic letter ‘nun’ as part of a world wide solidarity movement, to stand in solidarity with the Assyrian’s & other Christians in Iraq. If you’re unaware of the situation, the nun letter is the first letter of the Arabic word Nasrani/Nazarene which means Christian. The terrorist group ISIS have been marking the homes of Christian’s with this letter so as to easily identify them. They have been given the choice of convert, pay a tax or die by the sword.

the bottom symbol looks like the arabic letter for God. It might be an islamic or sikh symbols. The top is christian,