Russia and Ukraine’s superficial attempts to reconcile in Berlin earlier this week have rapidly come to nothing

Barely had the ink dried on another diplomatic attempt to bring peace to eastern Ukraine than a bloody explosion ripped through a trolleybus in Donetsk, killing 13 people.

Foreign ministers of Russia and Ukraine had signed a document in Berlin late on Wednesday night calling for Kiev’s forces and Russian-backed rebels to pull back artillery from the front lines: but on the ground, instead of peace, came signs of intensified violence.

The trolleybus had all its windows blown out, with pools of blood and shattered glass on its floor. There was also major shrapnel damage to a nearby building, and a separate impact nearby where a tram had been hit.

“I saw dead people on the floor, and injured women screaming for help,” said Ivan, a 74-year-old who lives in the building next to the blast. He had a cut face because of the flying glass from his windows, which had been blown out by the explosion. “It was a scene of total chaos.”

The Donetsk rebels have released a list of 13 victims of the attack, ranging in age between 23 and 76.

Facebook Twitter Pinterest Street cleaners shovel debris from the scene of a mortar strike on city bus. Photograph: James Sprankle/James Sprankle/dpa/Corbis

As has happened many times during the conflict, the two sides had starkly differing versions of the incident. Rebel gunmen on the scene said it had been carried out by a pro-Ukrainian diversionary group operating from within rebel territory. They later announced that those responsible had been detained, but there was no further information about who they were and how they were caught.

The impact craters suggested the incoming shell had come from the north-west, which meant it could have been fired from Ukrainian positions close to the airport. However, Ukrainian officials said their forces were located too far from the spot to be responsible, with the prime minister, Arseniy Yatsenyuk, calling it “a terrible act against humanity” committed by “Russian terrorists”.

The location did indeed appear to be out of mortar range for Ukrainian positions, though it also seemed unlikely that separatists would have any reason to carry out the attack. One local said the rebels had been repairing tanks in a factory across the street from the blast, which was perhaps the target. Others agreed that there was frequent movement of heavy armour in the immediate vicinity. There is also a Soviet-era military college, now used by rebel troops, nearby.

The gruesome pattern of the conflict has seen repeated attacks on ostensibly military targets go awry, leaving civilians dead. Earlier this month, 13 people died when a bus was hit while standing at a Ukrainian checkpoint, apparently after coming under rocket fire from rebel positions. At least 5,000 people have died since the conflict began last spring.

Kiev and the rebels, who are backed with Russian weaponry, signed a ceasefire deal in Minsk in September, but the accord has never been properly implemented. While there was a lull in fighting, clashes have intensified in recent days, with Ukrainian positions at Donetsk airport and Debaltseve coming under heavy fire, and the separatist town of Gorlovka shelled by Ukrainian forces.

“There is no ceasefire. We will fight. I promise,” rebel leader Alexander Zakharchenko told a weeping woman at the scene of the trolleybus attack. “We will move the front lines out further, so they can’t hit Donetsk any more,” he said later, suggesting a renewed rebel offensive is on the cards.

The deaths happened after Ukrainian forces admitted they had lost control of Donetsk airport on Wednesday, a symbolic battleground held by government forces throughout the conflict.

Recriminations are likely in Kiev as volunteer brigades heavily involved in the fighting criticised army generals for poor leadership and bad decision-making.

Russian journalists posted photographs of dead Ukrainian forces at the airport, and their bodies were later handed over to Ukrainian representatives. It is not clear how many Ukrainians died in the battle for the airport, with figures ranging from a handful to several dozen.

A Ukrainian soldier being treated in government-held Konstantinovka told monitors from the Organisation for Security and Cooperation in Europe (OSCE) that he and around 80 other soldiers at the airport had suffered similar symptoms: “Uncontrollable muscle spasms, vomiting and difficult breathing”. Some had become unconscious, he claimed.

The symptoms led many to wonder whether chemicals had been used during the fighting. A spokesman for the OSCE said the organisation was investigating further and was “not in a position to confirm or refute” reports of chemical use.

The rebels said they had captured 44 Ukrainian soldiers alive. In the afternoon rebel gunmen accompanied by their leader, Zakharchenko, arrived at the scene of the trolleybus attack, marching around a dozen Ukrainian prisoners along with them. The prisoners, bandaged and scruffy, were made to kneel on the asphalt close to where the blast occurred while angry locals assaulted them verbally and physically.

The rebels encouraged the filming of the incident, but ordered television crews to lower their cameras when five Grad multiple rocket launchers drove by, empty. Shortly afterward there were another two.

Grads, which can rain a shower of up to 40 rockets across a huge area, are notoriously imprecise and have been used by both sides, causing major damage to residential areas and civilian casualties.

One elderly man whose apartment windows were blown out said the Ukrainians and rebel forces were both idiots, and all he wanted was for the fighting to finish.

“What are we fighting for? Can’t we just go back to like it was before? I worked 30 years down a mine and never saw such awful things as I saw this morning,” said the man, who asked not to be named.

Like all pensioners, he has not received a proper pension for months, and is scraping by on around £30 per month provided by the rebels.

However, most locals reserved their anger firmly for the Ukrainian army, the government in Kiev and its perceived backers in the west. One elderly man wept bitter tears, shouting repeatedly that he wanted to travel to America to murder Barack Obama and his children.

The Ukrainian president, Petro Poroshenko, has blamed the violence in the east on Moscow, telling the World Economic Forum in Davos on Wednesday that 9,000 Russian soldiers are currently stationed in the region. Moscow insists there are none.

Poroshenko was due to meet Vladimir Putin in Kazakhstan last week, with the German chancellor Angela Merkel and the French president, François Hollande, but the summit was postponed. A western diplomat in Kiev said the main reason was because Merkel was irritated at the lack of commitment from Putin.

On Thursday in Davos, Merkel said there was no reason to lift sanctions on Russia as yet.

“Economic sanctions were unavoidable. They are not an end in themselves. They can be lifted if the reasons why they were introduced are removed. But unfortunately we are not there yet,” she said.

Instead, the foreign ministers of the four nations met in Berlin on Wednesday evening and agreed artillery should be withdrawn in accordance with a ceasefire agreement signed in Minsk in September. However, so far there has been little sign that a ceasefire can hold, and Thursday’s attack – combined with rebel vows to advance – gives little hope for peace.

The level of suffering in Donetsk in recent months and the anger towards Ukrainian forces makes it hard to imagine any kind of lasting political settlement taking hold. Even those who were previously sympathetic towards Kiev have grown fatigued of living under the daily stress of shelling. They feel abandoned and wish for the conflict to end, whatever the outcome.

“In France, 17 people were killed and millions came out on to the streets, the whole world was up in arms,” said Yulia, a doctor working at one of Donetsk’s medical institutions. “Here, 17 people were killed today alone, and nobody cares.”