Summing up the Kharkiv attack and what we know so far, via our newsroom:
Officials in Ukraine now say two people were killed and about 11 others injured when a bomb went off at a peace march in the government-controlled eastern city of Kharkiv.
Earlier, officials had said three people died in the February 22 explosion.
Police also said an unspecified number of suspects have been detained on suspicion of carrying out the attack, which struck a demonstration marking the first anniversary of the overthrow of former President Viktor Yanukovych.
The source of the explosion was not immediately known but Kharkiv police spokeswoman Natalya Zakharova called the blast an apparent "terrorist" explosion, a term Ukrainian officials use for the Russia-backed separatists in eastern Ukraine. A regional Ukrainian prosecutor posted online that the bomb had been thrown from a car.
A Guardian editorial urges a thorough debate on "the lessons of Ukraine" and defense and security:
The Lords committee report is a substantial analysis of the most dangerous piece of aggression in Europe for the past 20, perhaps even the past 50, years. What it says matters, not just as a piece of analysis of the recent past but as a signpost pointing well into the future. It argues that the EU should have seen the conflict coming and that it was slow to adapt to the realities of Russian strategy. Echoing a speech this week by the former MI6 chief Sir John Sawers, which argued for dealing with “the Russia we have, not the Russia we’d like to have”, it argues that western policy-making had become overly optimistic. It chides the Foreign Office and other EU states with loss of analytical capacity on Russia, including a decline in language skills and experience on the ground, which meant that the shifts in Moscow’s policy went underestimated. The net result, as Sir John put it this week, is “a wretched outcome for Ukrainians. But it may be the least bad attainable outcome”.
The report also details a serious failure of statecraft. It reveals the absence of a strategy to counter Vladimir Putin’s Russia while avoiding starting a worse war than the one that is still taking place in eastern Ukraine. That absence of strategy is not Britain’s fault rather than the EU’s, or vice versa. But Britain’s failure is part of it and it needs redressing. If that does not happen, the dangers of further opportunism, including against the Baltics, will mount. When Mr Cameron speaks to MPs on Monday about the latest developments in Ukraine, he should be held to account for Britain’s part in the failure. He should not pass the buck to the EU. But nor should he be allowed to rattle a sabre that proved to be blunt when it mattered. This is about real engagement with allies, not twice-reheated Churchillism.
All the UK political parties must face the implications of what has happened in Ukraine. The answers are certainly not all military. They are above all political and economic. But the experience poses military questions too, here as elsewhere. Those questions apply across Nato, where member states have reduced defence spending over the past five years by an average of 20% while Russia has increased its spending by 50%. In this country, events in Ukraine challenge the credibility of the current government’s public spending plans, which imply a 36% real-terms spending cut in defence in the coming parliament on top of the 11% cut in this one. Cuts on that scale would have implications that cannot be simply dismissed.
We are aware of a video circulating of the moment of the Kharkiv blast and its aftermath, but have deemed it too graphic and insensitive to the blast's victims to post. But if you believe the news value sufficiently compelling, we would note that you can find the video in @gullivercragg's twitter feed.
Other unconfirmed reports suggest the four suspects are Ukrainian citizens.
This report quotes Ukrainian security officials claiming that the bombers in Kharkiv were trained in Russia.