"We consider the serious incident, which occurred inside territory controlled and supported by Russia and illegally armed groups, a confirmation of Moscow's and its puppets' attempts to intimidate the OSCE and nullify the efforts of Ukraine and the SMM to stabilize the situation on the contact line," the ministry said in a statement.
"The news of the April 23 death of one and injury of several observers from the OSCE's Special Monitoring Mission (SMM) in the territory temporarily occupied by the Russian Federation in certain areas of Donetsk and Luhansk regions was met with deep pain and sadness in Ukraine," it said.
Ukraine's ministry expressed sincere condolences to the family of the deceased and wished speedy recovery to the injured.
It also called on Russia to fulfill its obligations under the Minsk peace agreements, to take all urgent measures in order to immediately stop provocations against OSCE observers, and to ensure full security of the SMM and its unhindered access to all occupied territory, including to the temporarily uncontrolled sections of the Ukrainian-Russian border.
"Ukraine will do everything possible to ensure an immediate, full and impartial investigation of the crime in order to bring the perpetrators to justice," the statement said.
Read alsoMember of security watchdog OSCE killed in Ukraine was American citizen – mediaSpokesperson for Ukraine's Ministry of Foreign Affairs Mariana Betsa expressed her condolences on Twitter on the same day.
"First SMM loss. Heartbreaking. Unarmed civilian mission. Brave people. Russia&proxies bear full responsibility. RIP," she tweeted.
As UNIAN reported, one American citizen was reported to have been killed in the OSCE car blast on Sunday morning near the occupied city of Luhansk in Ukraine's east. The area is controlled by the self-proclaimed Luhansk People's Republic ("LPR"). Later, the Ukrainian authorities reported he was a UK national. Two other observers – a German citizen and a Czech citizen – were injured and rushed to hospital.
The so-called "people's militia" of the "LPR" posted footage from the site of the incident.