Update as of 6:37 a.m. EDT: Russian Foreign Minister Sergei Lavrov accused Ukraine's interim government of not honoring the deal arrived at last week in Geneva, BBC reported.

"Extremists are calling the tune," Lavrov reportedly said, condemning a shooting on Sunday near Slaviansk, in eastern Ukraine, which claimed the lives of 3 people and criticized the protests in the capital city, according to BBC. Lavrov also reportedly accused Ukraine of not acting to disarm right-wing nationalist groups.

Nearly three people were killed in a gun attack on a Ukrainian city controlled by pro-Russian supporters, who continue to occupy government buildings in the country in violation of a deal struck in Geneva last week, while Russia blamed Ukrainian nationalists for the incident.

Separatists near the eastern Ukrainian city of Slaviansk said four vehicles had reached a checkpoint at about 2:00 a.m. local time (7 p.m. EDT) and opened fire on them to which they retaliated and killed two of the attackers, who they claimed belonged to a nationalist Ukrainian movement, Reuters reported. The deaths were the first in armed clashes in eastern Ukraine since a meeting in Geneva last Thursday between the U.S., European Union, Russia and Ukraine to end the violence in Ukraine.

"We had three dead, four wounded," Vladimir, one of the separatist fighters, told Reuters at the checkpoint. 

Russia expressed outrage at the shootings and blamed Ukrainian nationalists for attacking the separatists while Viktoriya Siumar, deputy secretary of Ukraine's national security council, said according to BBC, that "the level of criminality in eastern Ukraine has increased substantially recently," and expressed concerns about Russia’s accusation. Ukraine has said it will launch an investigation into the attack in Slaviansk, BBC reported.

The Thursday meeting between diplomats from Russia, U.S., Ukraine and other European countries in Geneva concluded with a deal, which requires illegal separatist groups to disarm and vacate all government buildings and public spaces. In return, pro-Russian protesters in eastern Ukraine will be pardoned, except for capital crimes, by Ukraine's government, which will start a public consultation program to pass on constitutional powers to the provinces. The U.S. has threatened Russia with more sanctions if the Geneva deal fails.

Vice President Joe Biden is scheduled to meet Ukraine's acting president, Oleksandr Turchinov, and Prime Minister Arseniy Yatsenyuk in Kiev on Tuesday to discuss further steps that can be taken by the international community to assist Kiev.