Macedonian police have arrested 20 "Islamist" terror suspects in connection with the lakeside murder of five men near the capital Skopje.
Interior Minister Gordana Jankulovska said the suspects were mostly Macedonian citizens and some would be charged with terrorism.
She said some had fought against Nato troops in Afghanistan and Pakistan.
The arrests came during raids by 800 police officers in Skopje on Monday. The killings took place last month.
There was no claim of responsibility for the lakeside attack, which rekindled fears of ethnic violence in Macedonia.
The victims were four men in their late teens and 20s and a 40-year-old.
In March there were clashes between youths from Macedonia's Slavic majority and the ethnic Albanian minority.
A peace deal was signed in August 2001 to end heavy fighting between the two communities in the former Yugoslav republic.