Nine wooden spikes topped with parts of a dead pig were planted on a plot of land where Muslims are planning to build a mosque in the eastern city of Erfurt, German police said Monday.

The 1.5 meter-tall (nearly 5-foot) stakes were topped with half of a pig's head, pig feet, and pig bowels among other things, the German news agency dpa reported. Police say whoever was responsible is unknown.

There have been repeated protests against the construction of the Ahmadiyya mosque in Erfurt, including one by protesters who erected large Christian crosses on a neighboring property.

A spokesman for the Erfurt community, Mohammed Suleman Malik, said in a statement to The Associated Press that "while such acts do not make us lose our composure ... we find it very sad that people go down to such a level."