Kabul, Afghanistan CNN  — 

The death toll from a suicide bombing in eastern Afghanistan Tuesday has risen to 68 people, with at least 165 others injured, officials said.

A suicide bomber detonated explosives amid a crowd of protesters outside a police station near the Pakistan border in the Momandara district of Nangarhar province, said provincial spokesman Attaullah Khogyani.

It’s not clear what the protest was about, nor who carried out the attack.

Men shout slogans against terrorists after a suicide attack among the protesters in Momandara district of Nangarhar province, Afghanistan, Tuesday, Sept. 11, 2018.

Last week, US Secretary of Defense James Mattis made an unexpected trip to Afghanistan as the US tries to make headway in the country after 17 years of war.

Mattis touched down in the country amid a bloody month in the prolonged conflict.

One US service member was killed and another was wounded on September 3 in “an apparent insider attack” – one carried out by a member of the Afghan security forces – in eastern Afghanistan, according to a statement from the NATO-led coalition in Afghanistan, Resolute Support. Ghani said that preventing these “green-on-blue attacks” was a “top national priority.”

Days later, 20 people – including two journalists – were killed in Kabul in twin bomb attacks on a wrestling club. ISIS claimed responsibility for that attack. A recent UN report said the number of Afghan civilians killed in the first six months of this year has reached a record high.

Earlier this month, US Secretary of State Mike Pompeo named veteran diplomat Zalmay Khalilzad as a newly-named State Department special envoy to Afghanistan.

Khalilzad, Pompeo said, would be “full time focused on developing the opportunities to get the Afghans and the Taliban to come to a reconciliation.”

CNN’s Jennifer Hansler and Ryan Browne contributed reporting.