Her eyes red, Valentina Chebanova sat opposite her seven-year-old granddaughter as a group of women and children waited to be bussed to Russia by rebels in Ukraine's southeastern city of Donetsk.

"I lived all my life here... I don't want to go to Russia forever," she said as she began to weep.

Seven miners were killed and two others are missing after a gas explosion ripped through an underground coal mine in eastern Ukraine, authorities said on Friday.

The blast happened before dawn on Thursday at a depth of 300 meters (1,000 feet), located in the eastern city of Kirovsk, the State Emergency Service said in a statement.

Ukraine's interior minister said on Friday that federal forces had inflicted "high casualties" on separatist rebels led by a Chechen commander in the southeastern port of Mariupol.

A loud explosion rang out in central Donetsk on Thursday evening followed by a series of smaller explosions that sounded like artillery, Agence France Presse journalists said.

The explosions were heard shortly after 10:00 pm local time (1900 GMT). A spokeswoman for the separatist Donetsk people's republic could not be immediately reached for comment.

Russian President Vladimir Putin held phone talks Thursday with his Ukrainian counterpart Petro Poroshenko on Kiev's plans for defusing the crisis in the separatist east.

"Ukraine's president notified Vladimir Putin of his plan to settle the situation in Ukraine's southeast," Putin's spokesman Dmitry Peskov told Russian news agencies.

A former Ukrainian presidential candidate and current backer of the pro-Russian separatist movement said Thursday he planned to ship food, medicine and money to the nation's war-ravaged east.

Oleg Tsarev, also previously a member of Ukraine's parliament, said while on a visit to the east Ukranian city of Donetsk that his People's Front movement had opened an office in Moscow and was preparing the first shipments of aid.

Russia said on Thursday it would submit a new draft resolution on Ukraine at the U.N. Security Council, saying it saw no progress in Kiev's efforts to defuse the crisis in the separatist east.

"In this resolution we would like to draw attention to the need for Ukraine to start implementing the OSCE chairman's 'road map' prepared on the basis of the April 17 Geneva agreement," Russian news agencies quoted Foreign Minister Sergei Lavrov as saying.

Russia accused Ukraine on Thursday of using "prohibited weapons" during its attempts to seize back control of the separatist stronghold city of Slavyansk, charges denied by Kiev.

The Russian foreign ministry's human rights ombudsman's comments came shortly after Moscow state media reported the use of incendiary bombs by Kiev's forces in the blockaded eastern city.

Nine miners were missing on Thursday after a gas explosion ripped through an underground coal mine in eastern Ukraine, authorities said.

The blast happened before dawn at a depth of 300 meters (1,000 feet) in the mine, located in the eastern city of Kirovsk, the State Emergency Service said in a statement.

Russian President Vladimir Putin warned Ukraine not to reject a reduced gas price offer but Kiev rebuffed the proposal as key EU-mediated talks to resolve the dispute ended in deadlock on Wednesday.

Moscow and Kiev exchanged barbs after nearly five hours of haggling in Brussels failed to yield a deal.