Hundreds of mourners attended an emotional memorial service in the German town of Duisburg this weekend for victims of the Love Parade festival.

German President Christian Wulff and Chancellor Angela Merkel were among the dignitaries who attended the memorial service, held at Salvator Church in Duisburg on Saturday July 31. Friends and relatives of those killed at the Love Parade festival were also present. As a mark of respect for the 21 people who died at the free music festival, July 24, flags across Germany flew at half-mast.

"We owe it to the victims and last but not least to ourselves that all what has happened has to be cleared up without gaps," said Hannelore Kraft, prime minister of North-Rhine Westphalia region at the memorial service, which was broadcast live on German television and also shown at churches, football stadiums and public spaces throughout Germany.

"How could something like that happen? Who is to blame? Who is responsible? These questions have to -- and will -- be answered," a clearly shaken Kraft went on to say.

Nikolaus Schneider, the president of the council of the Lutheran church in Germany, also spoke at the church service, calling the Love Parade "a death dance."

"In the middle of a celebration of the lust for life, death showed its ugly face to all of us," he went on to say during his sermon, which also criticized how the catastrophe had been handled.

Chancellor Merkel commented after the service: "The right conclusions must be drawn from this terrible incident of Duisburg."

Duisburg's mayor, Adolf Sauerland, who has been heavily criticized in the German media for allegedly ignoring safety warnings in the run up to Love Parade, did not attend the memorial service.

Before the service, church bells across Duisburg and neighboring cities rang in memory of those who died. In a mark of respect, hundreds of mourners also marched from the city's train station towards the tunnel, which had served as an entrance point to the Love Parade festival and where mass overcrowding and panic seemingly led to last weekend's loss of life.

Following the tragedy, which also resulted in over 500 people being injured, prosecutors have launched a criminal investigation to determine who was responsible for the disaster.