Polish and European officials joined thousands of people for the funeral of Pawel Adamowicz, the mayor of Gdansk.
Mr Adamowicz, 53, died on Monday after being stabbed the night before at a charity event. The arrested suspect is an ex-convict with a grudge against an opposition party that Mr Adamowicz once belonged to.
European Council President Donald Tusk, a personal friend of Mr Adamowicz, was among those attending the burial at the vast Gothic St Mary’s Basilica. Poland’s President Andrzej Duda and Prime Minister Mateusz Morawiecki also attended along with former leaders including Lech Walesa.
Other dignitaries included former German president Joachim Gauck and city mayors from other countries. The powerful leader of Poland’s ruling conservative party, Jaroslaw Kaczynski, was not in attendance.
The black urn with the mayor’s ashes will be laid to rest at one of the basilica’s chapels.
Crowds in the streets were able to watch the ceremony on giant screens.
A solemn procession brought Mr Adamowicz’s coffin to the basilica for a Mass on Friday night. The body was then cremated.
The killing, which came as Poland faces a deep political divide over actions by the ruling Law and Justice party, was a shock to the nation. It has drawn calls for greater national unity and condemnation of hate speech in the public sphere.