Seismic data adds to evidence that Ukraine's Kakhovka dam was ...

Evidence is growing that the Nova Kakhovka dam was blown up, after the publication of seismic data showing there was a blast at the site in the early hours of Tuesday morning.

Norsar, the Norwegian Seismic Array, said signals from a regional station in Romania pointed to an explosion at 2.54am. Norsar did not draw conclusions on who was responsible.

The Ukrainian government has said Russian occupying forces had control of the hydroelectric infrastructure on top of the dam and were using it as a garrison at the time of the blast. Explosive experts have said it would be much easier to blow up the dam from within than by firing on it from a distance.

On Friday morning, the Ukrainian security service published what it claimed was an intercepted phone call proving Russian responsibility for blowing up the dam on Tuesday.

The SBU posted a recording of a 90-second telephone conversation on the Telegram social media app, and claimed it was between two “occupiers”, the word normally used by Ukrainian officials for Russian soldiers.

The two men discuss the destruction of the dam, and one of them assumes it was carried out by Ukrainians but the other speaker corrects him, saying “our guys did it”.

“Our saboteur group is there. They wanted to cause fear with this dam. It did not go according to the plan. More than they planned,” the speaker said.

The authenticity of the call could not be verified. The SBU statement does not identify the speakers, nor does it indicate the time or place the call was supposed to have taken place. An SBU source said the call was intercepted on Thursday and that more details could not be provided as the recording was part of a criminal investigation.

Ukrainian officials have expressed frustration that Kyiv’s account of the dam’s destruction, that it was blown up from inside by Russian forces, has not so far been confirmed by US, UK or other intelligence agencies.

Ihor Syrota, the director general of the Ukrainian hydroelectric power company Ukrhydroenergo, dismissed suggestions the dam could have been destroyed as result of Ukrainian shelling or catastrophic structural failure as Russian propaganda.

“The plant was designed to withstand a nuclear strike,” Syrota told the Guardian in an interview in Kyiv. “To destroy the plant from the outside, at least three aircraft bombs, each of 500kg, would have had to be dropped on the same spot. The station was blown up from the inside.”

He added: “They brought hundreds of kilograms of explosives there. Ukraine reported last year that the station was mined. The Russians were just waiting for the right day to blow it up.”

President Volodymyr Zelenskiy held an online meeting with environmental activists from around the world to establish an expert group to rally international support to help recover from the ecological disaster caused by the dam’s destruction.

“Tens of thousands of birds and at least 20,000 wild animals are at risk of death,” he said. “Obviously, the Kakhovka reservoir has been turned into a huge graveyard for millions of living beings.”

He said it was becoming a global problem as contaminated flood waters flowed into the Black Sea.

In his nightly video address, recorded on a train after a visit to the flood zone, Zelenskiy thanked Ukrainian troops and repeated Kyiv’s earlier claims of military success around the city of Bakhmut. But he did not discuss the southern front, which so far appears to be the main focus of Ukraine’s emerging counteroffensive.

“We see every detail. But it’s not time to talk about it today,” he said.

Ukraine’s deputy defence minister Hanna Maliar said battles on the southern front were continuing for the settlement of Velyka Novosilka and that Russian troops were mounting an “active defence” at the town of Orikhiv.

Russian official sources and military bloggers reported intense fighting overnight and early on Friday morning around Orikhiv, south-east of the Ukrainian-held city of Zaporizhzhia.

Unverified videos posted online showed German-made Leopard tanks and US-made armoured personnel carriers in action on the Ukrainian side, and helicopter gunships on the Russian side. The unconfirmed accounts from Russian military bloggers portray small advances by Ukrainian forces at a high cost in casualties and loss of equipment.