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rtillery shells hit close to the center of Ukraine's separatist-held city of Donetsk for the first time on Thursday, a Reuters witness said.
People poured out of their offices onto the stairwell of the city's main administration building after loud explosions nearby triggered an evacuation warning.
A short while later, there were at least two further blasts near the city center following the whistling sound of incoming shells, a Reuters correspondent at the scene said.
This comes after, pro-Russian separatists said heavy shelling hit several neighborhoods around the rebel stronghold of Donetsk in eastern Ukraine where government forces are trying to tighten their grip.
Separatist Internet news outlet Novorossiya said Ukrainian forces hit targets in the Leninsky region of Donetsk and had struck regions to the east and southwest of the city in previous days.
The news outlet said the areas hardest hit were Makiyivka's Hirnitsky neighborhood as well as areas between Donetsk and Dokuchaevsk which lies south of the city.
There was no information on casualties. The United Nations on Wednesday put the overall death toll among Ukrainian forces, rebels and civilians at more than 2,000 since the beginning of the conflict in April when separatists seized state buildings across eastern Ukraine.
Ukrainian troops have been slowly encircling Donetsk, the regional hub with a peace-time population of nearly a million.
Meanwhile, a senior official of the International Committee of the Red Cross (ICRC) will travel to Kiev and Moscow for talks on the delivery of Russian aid to eastern Ukraine, an ICRC spokeswoman said on Thursday.
Laurent Corbaz, head of ICRC Operations for Europe and Central Asia, will stress the independent aid agency's "strictly humanitarian role" and that "the delivery of aid should not be politicised", spokeswoman Anastasia Isyuk said. Corbaz was expected to leave Geneva later on Thursday.
"The question of border crossing procedures and customs clearance (for the aid convoy) still have to be clarified between the two sides," Isyuk said.
A Russian aid convoy, which has aroused Kiev suspicions of a possible covert military action, was snaking its way through southern Russia, apparently heading to Rostov-on-Don, a Reuters witness said.
The pro-Western Ukrainian government and its Western allies accuse Moscow of arming the separatists who have set up 'people's republics' in Ukraine and say they want to join Russia. Moscow, while voicing support for the rebels, has denied it is arming them.
The Ukrainian government on Wednesday denounced the dispatch of the Russian convoy of 280 trucks as an act of "cynicism" and is insisting it be subject to tight controls and international supervision across the border into Ukraine.
On another note, Ukraine's parliament approved a law on Thursday to allow gas transit facilities to be leased on a joint venture basis with participation from firms in the European Union or United States.
Ukraine will hold 51 percent and foreign partners will be offered 49 percent in the venture, which would manage both transit pipelines and underground gas storage facilities.
UKRAINIAN SEPARATIST RESIGNS
The leader of the pro-Russian separatist rebels in Ukraine's Luhansk region has resigned, Russian state-run broadcaster Rossiya 24 reported on Thursday.
The resignation of Valery Bolotov was the second in seven days by a senior separatist official. The chief separatist in neighboring Donetsk region, Aleksandar Borodai, announced he was stepping down on Aug. 7.