JALALABAD, Afghanistan — A suicide bomber attacked an election rally on Tuesday in the eastern Afghan province of Nangarhar, killing at least 14 people and once again highlighting security concerns as candidates prepare for an Oct. 20 parliamentary vote amid a raging war.

The attack struck at a gathering of about 300 supporters of the candidate Nasir Mohmand in Nangarhar’s Kama district. Najibullah Kamawal, the province’s director of public health, said at least 43 others were wounded. Officials feared the toll could rise.

Mr. Mohmand survived, but with more than two weeks until Election Day, at least other seven candidates have already been killed across Afghanistan.

Nangarhar has seen a drastic increase in violence in recent years, with the emergence of the Islamic State, which has its foothold in the province, adding to insecurity caused by the Taliban. Corruption and a heavy infiltration of mafia have complicated the situation, so much so that after back-to-back suicide bombings in the provincial capital, Jalalabad, the government recently changed all senior police officials and handed control of security to the army.