The United Nations Security Council is due to meet on January 26 to consider a response to a deadly rocket attack on the East Ukrainian city of Mariupol that left up to thirty dead. Both Ukrainian and Western officials blamed the attack on Russian-backed rebels fighting in East Ukraine's Donbass region, while the Organisation for Security and Cooperation in Europe said that the rockets had been fired from rebel-held territory.

The Security Council held an emergency meeting to consider the attack on January 24, but Russia blocked a resolution on the attacks, Western diplomats said later.

US President Barack Obama, currently in India, warned of the possibility of increased Western sanctions on Russia following the rocket attack. “I will look at all additional options that are available to us short of military confrontation and try to address this issue,” he told a press conference in Delhi, adding that the rebels in East Ukraine had received “Russian backing, Russian equipment, Russian financing, Russian training and Russian troops,” as quoted by the Financial Times.

Donald Tusk, president of the European Commission and former Polish prime minister,  said on Twitter that the Mariupol attack suggested"appeasement encourages the aggressor to greater acts of violence".

The European Union's high representative Federica Mogherini said in a January 25 statement in response to the attack that the “further escalation of the open armed conflict” “would inevitably lead to a further grave deterioration of relations between the EU and Russia". She called on Russia “to use its considerable influence over separatist leaders and to stop any form of military, political or financial support". Mogherini has called an emergency meeting of EU foreign ministers for January 29.

Ukraine's President Petro Poroshenko told the emergency UN security meeting on January 24 that calls between rebels allegedly intercepted by Ukrainian intelligence proved the attack was masterminded "by terrorists who receive support in Russia".

Russian Foreign Minister Sergei Lavrov on January 25 blamed the violence on "constant shelling" by Ukraine government forces. "Lavrov pointed out that an escalation of the situation is a result of Ukrainian troops crudely violating the Minsk agreements by constantly shelling residential settlements," Russia's foreign ministry said in a statement.

According to observers from the Organisation for Security and Cooperation in Europe (OSCE) on the ground in Mariupol,  three multiple rocket salvos hit a residential area of Mariupol, on a Saturday morning when many residents were on the streets shopping. There was a Ukraine army checkpoint close to the site of impact of the three salvos of rockets, which were fired from at least two locations within rebel-held territory, over 15km to the east and to the north-east of the city, according to the OSCE.

Mariupol City Council reported up to 30 killed and 93  civilians wounded as a result of the attack, Mariupol City Council Secretary Andrii Fedai said.

Mariupol, with a population of around 500,000, is the largest city in East Ukraine's Donetsk region remaining under the control of Ukrainian government forces. It is a strategically important port on the Azov Sea used for crucial exports of iron ore and steel, and is itself also home to two large steel mills.

Alexander Zakharchenko, the self-proclaimed leader of the rebel “Donetsk People's Republic",  claimed on January 24 that the rebels had launched an offensive against Mariupol. He later denied any connection to the rocket fire or to ordering an invasion of the city. No further open hostilities were reported near the city, although Ukraine forces reported destroying a number of rebel rocket launchers.

The attack on January 24 followed a significant rebel victory on January 22, when government forces announced they were pulling out of Donetsk Airport, on the outskirts of the city of Donetsk, the largest rebel-held city.

The airport had been besieged by the rebels ever since peace accords were signed between representatives of the rebels, Ukraine and Russia in Minsk in September 2014. According to an alleged copy of a secret protocol to the Minsk peace accords defining the demarcation line between the conflict parties, which was published by Ukrainian media on January 24, control over the airport had been awarded to the rebels by the Minsk agreements.

Following the withdrawal of government forces, mortar fire struck Donetsk on January 23, killing 13 pedestrians and bus passengers. The rebels blamed the attack on government forces, while Ukraine's government blamed the rebels for staging the attack. On January 13, a rocket attack against a Ukraine government checkpoint at the town of Volnovakha, blamed on the rebels, killed at least 11 civilians in a bus. Rebels blamed the attack on Ukraine government forces.