RNA - Protesters in Zeta, outside the capital, Podgorica, pelted police with rocks, injuring four, and used a tree trunk to briefly block the road leading to Montenegro's main airport.
In the center of the city, police also used tear gas to disperse a crowd gathered near the Orthodox cathedral. Protests ended without incident in three other towns.
The rallies came after the Episcopal Council of the Serbian Orthodox Church, the dominant church among Montenegro's 620,000 residents, issued a statement urging believers to "gather in temples to pray ... and show we would not waver before the Montenegrin regime."
In a statement, Montenegrin police accused the church of instigating violence. "Statements of church dignitaries are leading to obstructions of public order and injuring of police officers," the statement said.
Under the law, adopted on Friday, religious communities must prove they owned property before 1918, when the Kingdom of Montenegro joined the Kingdom of Serbs, Croats and Slovenes, the predecessor of the now-defunct Yugoslavia.
If they can't prove ownership, the state will take over ownership of their property. The Serbian Orthodox Church says the Montenegrin state wants to seize its assets, something the government denies.
Montenegro's main opposition alliance, the pro-Serb Democratic Front, says the law promotes the small Montenegrin Orthodox Church, which is unrecognized by other major churches, at the expense of the Serbian Orthodox Church, which has around 12 million members, mainly in Serbia, Montenegro and Bosnia.
Montenegro's long-serving and pro-Western leader, Milo Djukanovic, has accused the Serbian Orthodox Church of promoting pro-Serbian policies to undermine Montenegro, a NATO member and a European Union membership candidate. Montenegro split from Serbia in 2006.
Serbia also wants to join the EU, but it refuses to join NATO and has pursued ties with Russia and China.
Most Montenegrins and Serbs share language and ethnic origins. Many Serbians have Montenegrin roots and families there.