On 13 April five slain Macedonian fishermen were discovered beside a lake at the village of Smiljkovci north of Skopje. Four of the victims were in their late teens or early 20s. The fifth was a man in his 40s.
Interior Minister Gordana Jankulovska said 20 people had been arrested in raids involving 800 police officers at more than 20 locations around the capital. Some would be charged with terrorism, and that the motive behind the attack had been "to spread fear", Jankulovska said. Most of those arrested were Macedonian citizens, she added.
"Some of them are followers of radical Islam ... and some are members of a group that fought in Afghanistan and Pakistan on the side of the Taliban against NATO troops," Jankulovska told a news conference.
The former Yugoslav republic has around 175 soldiers operating alongside NATO in Afghanistan, but its bid to join the alliance is blocked by a dispute with neighbouring Greece over its use of the name Macedonia.
Although it became an EU candidate in 2005, Macedonia has for seven years now been unable to start accession negotiations because over Greek concerns over the use of the "Republic of Macedonia" (see background).
Macedonia avoided civil war in 2001 when Western diplomacy halted fighting between government forces and ethnic Albanian guerrillas.
A peace deal offered Macedonia's Albanians, most of whom practice a moderate form of Islam, greater rights and representation, but the two communities still live largely separate lives.
In 2002, Macedonia's then government said police had killed seven "mujahideen terrorists" plotting to attack Western embassies in Skopje.
Prosecutors later said the dead were Asian migrants, killed in an elaborate plot hatched by the Interior Ministry to win favour with the West months after the September 11 attacks.
The August 2001 Ohrid Framework Agreement, brokered by Western powers and which halted the brinkmanship between the ethnic-Albanian communities in northern Macedonia (organised militarily in the National Liberation Army) and Macedonian forces will have to be "fully implemented" in order for the country to start accession talks, Peter Stano, a spokesman for Enlargement Commissioner Štefan Füle, said earlier this year.