(CBS News) DONETSK, Ukraine - The Ukrainian and Russian governments are reporting a deadly shootout at a checkpoint set up by pro-Russian insurgents in eastern Ukraine.
The armed clash appears to be the first since an international agreement was reached last week in Geneva to ease tensions in eastern Ukraine, where pro-Russian supporters have seized government buildings in at least 10 cities.
The Ukrainian Interior Ministry said one person was killed and three wounded in the shootout early Sunday near the city of Slovyansk. It said details of the incident were not yet clear. Reuters is reporting that witnesses said two people were killed in the shootout, although it is not clear on which side the casualties occurred.
In Moscow, the Russian Foreign Ministry blamed the clash on the Right Sector, a nationalist Ukrainian group that has supported the interim government in Kiev, the capital.
The Right Sector denied any role, saying Russian special forces were behind the clash, Reuters reports.
After the deaths, Russia questioned whether Ukraine's Western-backed government was complying with the Geneva agreement.
The fault for the failure of the Geneva agreement could determine whether or not the United States and its European partners impose tougher sanctions on Russia.
The deal signed in Geneva last week by the European Union, Russia, Ukraine and the United States agreed that illegal armed groups would go home.
So far, the pro-Russian militants have shown no signs of budging, though there was some hope of progress after Kiev said it would not move against the separatists over Easter, and international mediators headed to eastern Ukraine to try to persuade them to disarm.
CBS News met with pro-Russian separatists who have no intentions of leaving the public buildings they've taken over.
They've occupied a building in Donetsk for nearly two weeks, and have barricaded themselves inside with razor wire. The insurgents are demanding a separate state, or at least more autonomy for their region.
They are suspicious of Ukraine's pro-Western government in Kiev, and want closer ties with Moscow.
They have now begun calling themselves the Republic of Donetsk. In the republic's offices CBS News met spokeswoman Yekatarina Mihaylova.
Mihaylova told CBS that they will only leave if there's a referendum on the future of eastern Ukraine, and if rival protestors in the capital Kiev also go home.