“I am dismayed and appalled by this barbaric deed. It is still too early to know who is behind this murder, but it is quite clear that there are forces in Pakistan with an interest in undermining stability and working against the country’s democratic forces,” Bildt said in a statement on Thursday.
“Pakistan can only achieve security and stability through democratic development,” he added.
Bhutto was murdered by a lone gunman as she left an election rally in Rawalpindi, Pakistan, on Thursday. The gunman was reported by news agencies to have blown himself up after shooting the former prime minister. It is not yet clear whether elections planned for January will now go ahead.
Swedish opposition leaders also expressed distress at the assassination.
Mona Sahlin, leader of the opposition Social Democrats, said she received news of the murder with “shock and distress.”
“Benazir Bhutto was a great leader. She had many years left of her struggle to create prosperity in Pakistan and in Asia at large. The murder is a strike at democracy everywhere.
“As one of the few female party leaders in the world she was a great role-model and gave hope to women in Asia and the rest of the world,” Sahlin said.