Ukraine's separatist-held city of Donetsk experienced its most serious shelling in months over the weekend, as concerns mounted that both sides may be preparing military offensives.
Witnesses said intense artillery fire - the worst since a ceasefire was agreed in September - began in the early hours of Saturday and continued through yesterday.
A two-month ceasefire to end a war that has killed 4,000 people has appeared shakier than ever in the past few days, with both sides accusing the other of having violated the peace plan.
The fighting in Donetsk appears to be centred on the airport, to the north of the city, where a Ukrainian garrison has been fighting a defensive action against besieging rebel forces for two months.
The artillery fire appeared to be coming from both separatist and Ukrainian positions.
Fighting has intensified since rebels held leadership elections last week, prompting Ukraine to scrap a law granting devolved powers to eastern regions.
The two sides described each other's moves as fatal violations of the ceasefire signed in Minsk on September 5, but, despite fighting at the airport and several other flashpoints, neither side has so far resumed major offensive operations.
Yesterday's intensification of fighting follows the arrival of multiple military convoys into the Donetsk area over the past week, fuelling speculation that Russian-backed separatist forces are readying for a fresh offensive.
Ukraine said on Friday that 32 tanks, 16 howitzers, and 30 lorries had crossed the border from Russia near the separatist-held city of Luhansk. While it was impossible to verify the report, independent witnesses have seen several large military convoys featuring unmarked army trucks over the past two weeks.
In the latest incident, journalists working for the Associated Press spotted more than 80 Kamaz military lorries without numberplates moving in three separate convoys on Saturday.
The vehicles were crewed by men in dark green camouflage uniforms without insignia. Many of the trucks were pulling high-calibre artillery, the journalists said. The convoys were spotted near Donetsk and the town of Snizhne, 80km east.
The OSCE, which maintains a monitoring mission in Donetsk, said it had seen 40 vehicles, including 19 lorries hauling howitzers, near Makeevka, 15 miles north-east of Donetsk. (© Daily Telegraph, London)