Kiev

Romanian President Traian Basescu said at the presidential Cotroceni Palace late on Sunday that he 'categorically' disagrees with Ukraine's President Petro Poroshenko, who had said on Saturday Russia could shortly conquer Bucharest.

Twelve warships from NATO and other countries are to stage naval exercises, known as Sea Breeze, in the Black Sea.

Hosted by Ukraine, the drills are led by the US.

The maneuvers are held on an annual basis (and have been since 1997) and are not related to the developments in Ukraine and its standoff with Russia.

Russian Prime Minister Dmitry Medvedev has announced Moscow could restrict the movement of foreign flights in its airspace if new sector sanctions are introduced against the country.

"If there are sanctions related to energy [or] further restrictions to our financial sector, we have to respond asymmetrically," Russian agency ITAR-TASS quoted Medvedev as saying.

Leaders of self-proclaimed Donetsk and Lugansk People's Republics have urged the Organization for Security and Cooperation in Europe (OSCE) to ensure control over the ceasefire observance in southeast Ukraine.

Kiev officials and representatives of pro-Russian rebels have signed a ceasefire agreement at their meeting in Minsk, Friday.

Heavy fighting around flashpoint cities in eastern Ukraine on Sunday threatened the collapse of a tenuous truce between government forces and pro-Russian rebels less than 48 hours after it came into force.
      

Gunfire and heavy shelling rocked a key frontline city in eastern Ukraine overnight, raising fears on Sept. 7 that a tenuous truce between government and rebel forces had already collapsed.
     

Kiev officials and representatives of pro-Russian rebels have signed a ceasefire agreement at their meeting in Minsk.

Ukrainian President Petro Poroshenko said a ceasefire plan aimed at ending a near five-month conflict in the east of the country would be signed on Friday.
      
"Tomorrow in Minsk a document will be signed providing for the gradual introduction of the Ukrainian peace plan," he said on the sidelines of the NATO summit in Wales on Thursday.
      

Pro-Russian rebels in Ukraine's east have said they are ready to lay down arms if Kiev officials sign a plan outlining the steps to peace.

Russia will be facing increased pressure if it does not backtrack on its actions in the east of Ukraine, NATO has warned in the eve of Thursday's Wales summit.

As the meeting of NATO members' Presidents kicks off, the Ukraine crisis is expected to top the agenda, alongside the Sunni militant group Islamic State (IS) ad troops' withdrawal from Afghansitan.