Church bells have tolled across the Czech Republic as the country holds a national day of mourning for the victims of Thursday's mass shooting at a university in Prague.

A minute’s silence has also been held for the victims who died when a 24-year-old student, David Kozak, opened fire at Charles University, killing 13 people and then himself. Another person died in hospital later.

Students have lit thousands of candles at makeshift memorials at the arts faculty where the shooting took place.

The country’s prime minister, Petr Fiala who attended a mass at Prague's St Vitus Cathedral, said: “It is hard to find the words to express condemnation on the one hand and, on the other, the pain and sorrow that our entire society is feeling in these days before Christmas.”

In a telegram, Pope Francis assured the country of his prayers and said he is “deeply saddened” by the shooting. He entrusted "those who have died to the loving mercy of Almighty God" and invoked "divine strength and consolation upon their grieving families and friends."

In a statement, Charles University said: “We mourn the loss of life of members of our university community, express our deepest condolences to all the bereaved and our thoughts are with all those affected by the tragedy."

The gunman is believed to have killed his father earlier on that day and police are investigating his links to a separate double murder earlier this month.