Two years after 48 people died in an arson attack in Odesa as Ukraine's mixed allegiances erupted in violence, the situation is again fraught in the historic port city. Police and national guardsmen deployed in force on May 2 to prevent a repeat tragedy or worse in the next days, while feuding between local power brokers magnifies other fault lines running across Ukraine.

A backdrop to the events is the unanswered question of when those responsible for these deaths - and others in 2014, including more than 100 protesters and 20 police officers killed in Kyiv - will finally be identified and punished?

"All those responsible for the crimes must be brought to justice," EU ambassador to Ukraine Jan Tombinski said in a statement marking the May 2 anniversary date in Odesa. "I urge the government of Ukraine to follow up on the recommendations of the Council of Europe International Advisory Panel and to carry out an independent and transparent investigation."

Today, as well as lingering pro-Europe vs pro-Russia sentiment that propelled past events, it's also about struggles playing out in many parts of the country: vested local interests, corruption, and (in)subordination to Kyiv's writ.

At the root of recent tensions in Odesa – in which protesters were beaten and there was a grenade attack on a bank – is the clash between the city's mayor Gennady Trukhanov and the Odesa region governor (and former Georgian president) Mikheil Saakashvili. The governor, appointed by President Petro Poroshenko last summer to break clan control of the strategic Black Sea port area, successfully appealed to the president for the deployment of national guard units before May 2.

Trukhanov, rattled by recent (and violently dispersed) protests outside his offices, called for people not to join public actions on this emotive date, citing purported threats to burn down the city hall. The mayor called the situation "alarming" and pointed to differences between the city and regional administrations. In turn, Saakashvili warned Poroshenko of the danger of state collapse from renewed violence in the city.

A total of 3,500 police and 300 Ukrainian SBU security service agents and counter-terrorism operatives will maintain order in Odesa during a week of anniversary-related events. The SBU will also secure entrances to the city and border checkpoints, especially those on the border with Transnistria and Moldova.

Volatile ground

Odesa, known mainly to the world from Sergei Eisenstein's 1925 naval mutiny film epic "Battleship Potemkin", witnessed one of the most horrific manifestations of the unrest that swept the country in early 2014 amid the ouster of Ukraine's pro-Moscow president Viktor Yanukovych.

As the country was torn along fault lines of ethnicity and allegiance by the Maidan protests in Kyiv, and before the full eruption of the separatist conflict in East Ukraine, tensions flared in brutal fashion in Odesa on May 2. Maidan participants, soccer fans and rightwing militants marched through the city and clashed with supporters of federalisation that would grant more autonomy to Russian-speaking regions. This culminated in Odesa's House of Trade Unions being set on fire and the resultant deaths of dozens of pro-federalisation marchers holed up inside.

Two years later, as Kyiv sent extra law enforcers to Odesa for the anniversary, the Russian Foreign Ministry's Commissioner for Human Rights, Democracy and the Rule of Law Konstantin Dolgov condemned the deployment's inclusion of ultra-nationalist paramilitaries as "another provocation".

"Do they want to repeat the crime? Dolgov said. "All this is happening against the background of Kyiv's odious unwillingness to objectively investigate the Odesa massacre and punish the real perpetrators. And the West keeps silent as usual."

Key accusations against law enforcers boil down to the fact that they did not prevent the clashes on May 2. There are also many questions for the emergency services, which could have reached the burning building in five minutes, but took about an hour to arrive.

Bigger power plays go on

Meanwhile, the power plays that in recent months fuelled Ukraine's political chaos and paralysed its government continue unabated, despite the recent appointment of a new government under Prime Minister Volodymyr Groysman.

On the contrary, critics say that in choosing his ally Groysman, Poroshenko has chosen to perpetuate the existing situation where big business rules the roost of Ukraine's politics, despite the exhortations of the EU and US to reform and start afresh and transparently.

At the same time, issues connected with the country's deeper integration into the EU have repercussions at the regional level, including in Odesa, where Saakashvili's further tenure as governor has come under question.

For now, the wind seems to be blowing in his favour: Saakashvili just announced a major political win with Poroshenko's public support for his Road to Romania project to build a four lane 260-kilometre road from Odesa to the EU neighbour state. The route is expected to be used by up to 22,000 vehicles a day at a construction cost of $4.6bn to be shared by Ukraine, Romania and the EU.

Groysman also announced a national customs reform programme that will tie into Saakashvili's development plans for Odesa Port, thereby strengthening the governor's hand against opponents' attempts to force him out of office.