Moscow, Sha'ban 17, 1436, Jun 4, 2015, SPA -- At least 17 people were reportedly killed Wednesday in eastern Ukraine in the bloodiest fighting since the February ceasefire, according to dpa. The Ukrainian government and pro-Russian separatists traded blame for the escalation, which was predominantly within the partially rebel-held Donetsk region. A Donetsk rebel leader said the Ukrainian military killed 15 people including an unspecified number of civilians during seven hours of fighting. "The Ukrainian side carried out a provocation, opening fire on our positions across the entire front," Vladimir Kononov of the self-proclaimed Donetsk People's Republic said in comments carried by the Interfax news agency. Ukrainian Prime Minister Arseniy Yatsenyuk blamed Russia for the violence, saying that "today Russia has once again violated the [ceasefire] agreement. ... Its terrorists began a military operation." Ukrainian military spokesman Andriy Lysenko blamed the rebels for launching an attack to advance into government-controlled parts of the region. In the neighbouring Luhansk region, an elderly couple was killed early Wednesday when mortar fire hit their car in a Ukrainian government-held location, about 20 kilometres from the front line, the region's governor, Hennadiy Moskal, said on his website. The US government blamed Russia for the attacks, saying Moscow "bears direct responsibility for what's happening." State Department spokeswoman Marie Harf said the attacks were carried out by "combined Russian-separatist forces" on the Ukrainian side of the cease-fire line. "They have reportedly utilized grad rockets and other heavy weapons that should have been withdrawn under the February Minsk plan," Harf said. She said the Russian separatists reportedly killed one person, and said the number of injured Ukrainians was 20. She cited the Organization for Security and Cooperation in Europe (OSCE) as one of the sources for the casualty information. Attempts to seize additional Ukrainian territory will be met with more sanctions, she said. "We'll continue to impose additional costs, and we're having those conversations internally, certainly, and with our partners," Harf said. More than 6,400 people have died in the Ukraine conflict since fighting began in April 2014, according to estimates by the United Nations. The separatist rebellion erupted last year in Ukraine's two eastern-most regions after the country's former pro-Russian president Viktor Yanukovych was ousted amid mass protests in Kiev by groups calling for closer ties with the European Union. --SPA 00:46 LOCAL TIME 21:46 GMT www.spa.gov.sa/w