( CNN ) At least 30 people , including two children , have been killed in shelling in the southeastern Ukrainian city of Mariupol , city officials said Saturday , in the latest violence to rock the disputed Donetsk region . Another 102 people were injured , at least 75 of whom needed hospital treatment , and many suffered shrapnel injuries , Mariupol City Council said . Pro-Russian separatists are blamed for the attack on residential areas in the port city , Donetsk regional police chief Vyacheslav Abroskin said on his Facebook page . The Interior Ministry said one person was arrested in connection with the attack . Based on preliminary assessments , the shells were fired from Grad rocket systems , a statement from Mariupol City Council said . The statement also said the situation was under control , and urged residents not to panic but to rely on information from official sources only . Monitors with the Organization for Security and Co-operation in Europe said they conducted a crater analysis which showed the use of Grad and Uragan rockets that likely originated from areas controlled by the pro-Russian rebel group Donetsk People 's Republic ( DPR ) . The shelling comes amid a surge in fighting between government forces and pro-Russian separatists . U.S. Secretary of State John Kerry warned of increased international pressure on Russia . `` We call on Russia to end its support for separatists immediately , close the international border with Ukraine , and withdraw all weapons , fighters and financial backing , '' Kerry said in a statement . The White House says Vice President Biden spoke with Ukraine President Poroshenko on Saturday . They `` expressed grave concern over Russia 's blatant disregard for its commitments under the September Minsk agreement and unilateral escalation of the conflict , '' the White House said . The two leaders vowed to `` ensure that the costs continue to rise on Russia for its aggressive actions against Ukraine . '' Thousands have been killed since the conflict broke out in the spring of last year and a ceasefire agreed to in September in Minsk , Belarus , crumbled long ago . U.S. officials took to Twitter to condemn the latest violence . `` Today 's indiscriminate shelling of Mariupol ( is ) part of an apparently Russian-backed general offensive in complete violation of Minsk agreements , '' said U.S . Ambassador to Ukraine Geoffrey Pyatt . `` Russia 's escalation continues -- Kremlin 's callous disregard for human life ( incl Russian soldiers ) on full display in Ukraine , '' said Daniel Baer , the U.S. ambassador to the Organization for Security and Cooperation in Europe ( OSCE ) . The foreign ministers of Ukraine and Russia met this week in Berlin to discuss a way out of the violence . But despite the talks , violence in the breakaway Donetsk and Luhansk regions shows no sign of abating . Thursday 's shelling of a transit stop in Donetsk city -- an attack that Ukraine 's Defense Ministry blamed on rebels -- killed eight civilians , according to state news reports . But Ukrainian troops have come under heavy fire as well . That includes 115 attacks in a recent 24-hour period that killed three troops and wounded 50 more , Ukrinform , the Ukrainian national news agency , reported Friday . The OSCE monitoring mission in Ukraine condemned continuing fighting in civilian areas in a statement Saturday and urged both sides to refrain from using force in such areas , including near Donetsk airport . `` Using residential areas as firing positions attracts counter-firing to these areas , further endangering the lives of civilians , '' it said . `` All parties need to take robust and immediate action in order to end the new escalation in fighting and its heavy toll on civilians . '' Opinion : Time to rethink Ukraine deal . Ukraine and the West accuse Russia of sending troops and equipment over the border . In a bid to put pressure on Moscow over Ukraine , the United States and European Union have imposed financial sanctions against Russian interests . Wednesday , for instance , Ukrainian President Petro Poroshenko said `` more than 9,000 Russian troops ( crossed ) our Russian-Ukrainian border , bring with them hundreds and hundreds of tanks , armed personnel carriers , and killing Ukrainian civilians and attacking Ukrainian troops . '' Moscow denies the claims . Russian President Vladimir Putin blamed the wave of recent casualties on those giving the order to fire in heavily populated areas , in remarks reported by the state-run Itar-Tass news agency Friday . `` Those who give such criminal orders bear responsibility for this . People doing that should know that there is no other way of resolving such conflicts than peace negotiations and political measures , '' he said . Putin also suggested Ukraine was not interested in finding a peaceful resolution to the crisis and said he hoped `` common sense '' would prevail . The conflict in eastern Ukraine broke out after Russia annexed Ukraine 's southeastern Crimea region , as pro-Russia separatists claimed control of the Luhansk and Donetsk regions . From mid-April 2014 to January 21 , the conflict killed at least 5,086 people and injured at least 10,948 others , according to the United Nations . `` We fear that the real figure may be considerably higher , '' the Office of the U.N. High Commissioner for Human Rights said about the death toll in a report released Friday . No truce with Ukraine , rebel leader says . CNN 's Alla Eshchenko and journalist Victoria Butenko contributed to this report .
U.S. Secretary of State John Kerry calls on Russia to end separatist support . OSCE monitors say rockets were likely fired from pro-Russian rebel territory . The U.N. Security Council is expected to discuss the situation in Ukraine at a meeting Tuesday.