Two people died and more than 100 have been injured after two explosions at a Kurdish party election rally in south-east Turkey, the agriculture minister, Mehdi Eker, said.

The blasts occurred five minutes apart on Friday at the final election rally of the pro-Kurdish Peoples’ Democratic party (HDP) as the party leader, Selahattin Demirtaş, was preparing to address the crowd in Diyarbakir, the main city in Turkey’s predominantly Kurdish south-east.

It wasn’t clear how many of the injured were seriously hurt. Health minister Mehmet Müezzinoğlu earlier said about 50 people were injured, with 20 to 24 of them being treated in hospitals.

Supporters carry a wounded man at a Kurdish Peoples’ Democratic party rally in Diyarbakir. Photograph: Emre Tazegul/AP

Rally organisers first said a malfunctioning power distribution unit caused the explosions, but the energy minister, Taner Yildiz, later dismissed that explanation. He said they were caused by “external interference” with the power unit, though he did not say whether he believed a bomb was involved.

The explosions come at a tense time, two days before Sunday’s parliamentary elections in Turkey, in which Kurdish votes will be critical.

The party is vying to pass the threshold of 10% of total votes required to take seats in parliament. If it succeeds, it could make it impossible for the ruling Justice and Development party (AKP) to reach a “super-majority”. That would scuttle the AKP’s ambitions to change Turkey’s parliamentary system, using a new constitution, into a presidential system that could give President Recep Tayyip Erdoğan executive powers.

The prime minister, Ahmet Davutoğlu, said authorities would investigate the cause of the explosions.

“Whatever is behind this incident – whether it was a power transformer explosion, an assassination attempt, an act of provocation – we shall investigate it,” he said. “I call on my brothers in Diyarbakir: please beware of exploitation of the incident and provocations. No one should be involved in provocations.”

The rally was cancelled but a large group of youths remained at the site, protesting against the explosions. Some threw stones at a police water cannon that moved in to disperse the crowd.

Demirtaş urged calm. “Whatever the cause, I invite the people to retain their common sense,” he told CNN-Turk television. “Whatever happens, Turkey is in need of peace.”

He said some of the injured had lost limbs.

Earlier this week, assailants fired on an HDP campaign vehicle, killing its driver. Last month, bombs at two HDP offices injured six people in southern Adana and neighbouring Mersin.