Islamic State militants are claiming responsibility for a terrorist attack in Pakistan on Sunday that left dozens of people dead.

Condemnation is pouring in from the upper tiers of the United Nations.

Farhan Haq is Deputy Spokesperson for the UN Secretary-General.

He says Antonio Guterres denounces all terrorism and targeted attacks on civilians, and stands in solidarity with the government and the people of Pakistan.

A suicide bomber struck at a political rally in a northwestern area near Afghanistan.

Local health officials say at least 45 people were killed and more than 60 hospitalized.

The Islamic State-affiliated Amaq news agency says a member of the militant group detonated his explosive jacket in the middle of a crowd.

The agency goes on to say the attack is part of a war against democracy, and a rejection of Pakistan's electoral system.

Political parties in the country are gearing up for a lower house election later this year.

Sunday's attack only raises concerns about more bloodshed in the coming weeks.