A gunman opened fire at a campaign truck carrying Pakistan’s former Prime Minister, wounding him slightly and killing one of his supporters.

A gunman opened fire Thursday at a campaign truck carrying Pakistan’s former Prime Minister Imran Khan, wounding him slightly and killing one of his supporters, his party and police said. Nine others were also wounded.

Party official Asad Umar said Khan was wounded in the leg and was not seriously hurt. The identity of the gunman, who was arrested at the scene, was not immediately known. No group has claimed responsibility for the shooting.

The attack raised new concerns about growing political instability in Pakistan, a nuclear-armed nation with a massive population of 225 million people. Since his ouster in a no-confidence vote in Parliament in April, Khan has been able to mobilize mass rallies across the country, where he has whipped up crowds with claims that he was a victim of a conspiracy by his successor, Prime Minister Shahbaz Sharif, and the United States.