Afghan police arrested nine people accused of arranging suicide bombings, and separately detained 12 Taliban militants who were allegedly planning attacks west of Kabul, officials said.
The US military also said American and Afghan soldiers arrested two suspected midlevel commanders of the radical Hezb-e-Islami group of Afghan warlord Gulbuddin Hekmatyar, including an expert bomb maker.
The arrests come amid a spike in militant attacks across Afghanistan carried out by resurgent Taliban fighters and allied Islamic extremists.
The nine were detained Friday in the eastern Logar province and transferred to Kabul for allegedly helping Afghan and Pakistani militants prepare for suicide attacks, said Taj Uddin, spokesman for Afghanistan's counterterrorism department.
"We have reports that four suicide bombers were aided by this group and coming from Logar," said Uddin, who added one of the hour was killed in a recent attack on the Jalalabad-Kabul road.
Uddin had no details on whether the group was linked to a Friday suicide bombing in Kabul that killed at least 16 people, including two US soldiers.
Logar province tribesmen rejected the claim that the detainees, including a child aged about 15 and an elderly man, were part of a militant cell.
"They had a dispute with a man in their village, who accused them of being involved with suicide bombings," said Haji Alkum, who traveled from Logar to Kabul to try ensuring their release.