The OSCE, which has been monitoring the presidential election, says that despite flaws, and the terrible security situation, overall the election went fairly smoothly:

The 25 May early presidential election in Ukraine was characterized by high voter turnout and the clear resolve of the authorities to hold what was a genuine election largely in line with international commitments and with a respect for fundamental freedoms in the vast majority of the country. This was despite the hostile security environment in two eastern regions and the increasing attempts to derail the process by armed groups in these parts of the country. The Central and other election commissions operated impartially and collegially on the whole, although a number of transparency issues arose just prior to election day and decisions taken may have been beyond their authority. The voting and counting process were transparent and largely in line with procedures, despite large queues of voters at polling stations in some parts of the country. The early stages of the tabulation process were evaluated less positively by International Election Observation Mission (IEOM) observers mostly due to technical problems.

The election took place in a challenging political, economic and in particular security environment. Genuine efforts were made by the electoral authorities to conduct voting throughout the country, despite continued unrest and violence in the east of Ukraine, where anti-government forces control some areas, and the acting government is conducting counter-insurgency operations. This seriously impacted the election environment and affected the general human-rights situation there, also

obstructing meaningful observation. The election did not take place on the Crimean peninsula, as it is not under the control of the Ukrainian authorities, and citizens residing there faced serious difficulties to participate in the election…

In most of the country, election day took place peacefully. The CEC put voter turnout at 60 per cent. It started posting detailed preliminary election results by polling stations on its website on election night. Despite efforts of the election administration to ensure voting throughout the country, polling did not take place in large parts of Luhansk and Donetsk oblasts, due to systematic disruption by armed separatist groups. The voting and counting process was orderly and well organized in most of polling stations observed, with only minor procedural problems noted. However, the high number of voters frequently resulted in overcrowding, especially where local elections were held simultaneously, and frequently delayed the count in these polling stations. The early stages of the tabulation process were assessed negatively in a fifth of observations from IEOM observers, mainly due to working conditions, overcrowding, and an attack on the CEC’s computer system that disrupted the processing and transmission of election results.