KABUL — Twenty Afghan police officers were killed in two attacks Wednesday, including a mass poisoning, in southeastern Afghanistan.

In Ghazni Province, 17 Afghan officers who had just been trained by 12 Americans were drugged into stupors by comrades, described after the episode as Taliban infiltrators, while on duty. They were then shot to death in what appeared to be the single worst episode in a string of similar attacks, according to Afghan officials and an insurgent spokesman.