Nine mosques across the Netherlands received hate-filled letters smeared with what appeared to be blood, alarming Muslim communities and prompting outrage, local media reported Friday.

The mosques targeted are located in Rotterdam, Eindhoven, Arnhem, Tilburg, and The Hague, according to Dutch daily AD.

The letters contained defamatory language, insults, and cartoons of the Prophet Muhammad - seeking to insult by flouting Islam’s ban on such representations.

"This is a form of intimidation and threat,” Joram van Klaveren of the national mosque association K9 told public broadcaster NOS.

"The letters are full of hate rhetoric. In Rotterdam, one letter even referred to the ‘last days of Islam in Europe’.”