Ukraine crisis: Peace deal in 'great danger' as fierce fighting continues just hours before midnight ceasefire

Shelling and artillery fire has been reported as both sides engage in last-minute scramble for territory

Ukraine’s president has warned that an agreement to end the fighting ravaging the country is in “great danger” just hours before the ceasefire is due to take effect.

Battle's raged on Saturday, as Russia-backed separatists and Ukrainian forces rocketed each other, with shelling extending far beyond any front lines, as the clock ticked down to the agreed ceasefire of midnight.

Russian president Vladimir Putin and Ukrainian leader Petro Poroshenko signed an agreement on Thursday morning, after 16 hours of laborious talks, raising hopes for the end of a conflict that has claimed over 5,000 lives.

But today, president Poroshenko accused Mr Putin of “significantly increasing” the Russian offensive after reports emerged of 40 tanks and almost 100 heavily armoured vehicles and missile launchers crossing the Ukrainian-Russian border yesterday.

Shelling has been heard in rebel-held city Donetsk today, with correspondents reporting that fierce fighting has continued around Debaltseve.

Debaltseve is a key transport hub in the east of the country. Although it is presently held by Ukrainian forces, the town has been surrounded by rebel forces in recent days.

Kiev claims that the pro-Russian separatists have received orders to take both Debaltseve and Mariupol before the ceasefire is implanted.

In the 24-hour period in the run-up to the ceasefire at midnight this evening, the transport hub has been battered by rocket and artillery salvos.

Shells rained down Saturday afternoon on the government-held town of Artemivsk, 40 kilometers (25 miles) north of Debaltseve, striking a school, which rapidly burned to the ground.

Associated Press reporters also saw an artillery barrage near the town of Svitlodarsk, 20 kilometers (12 miles) north of Debaltseve, as well as considerable movement of Ukrainian forces' armored vehicles and rocket launchers along the road.

An undated satellite image released Saturday by the Ukrainian government showed a 5-kilometer (3-mile) long cloud of black smoke hovering above Svitlodarsk, evidence of what it said was the scale of rebel shelling.

Russia has repeatedly denied repeated Western claims that it has sent troops and equipment to the rebels. But on Saturday, the U.S. ambassador to Ukraine, Geoffrey Pyatt, posted on Twitter what he said were satellite photos showing Russian artillery systems near the town of Lomuvatka, 20 kilometers (12 miles) northeast of Debaltseve.

The Kremlin has continued to deny its involvement in the conflict, claiming Russia would act only as a guarantor in the peace process and could not affect developments on the ground.

Approximately 26 people are thought to have died in the region over the last few days.

Although many civilians have fled – a recent UN report claimed nearly one million people have been internally displaced because of the conflict – more than a dozen civilians are reported to have died in the recent shelling.

Events are an eerie shadowing of the failed September ceasefire agreement.

Many in the country fear the coming ceasefire will not hold.

Mr Putin and Mr Poroshenko are expected to discuss the issues over the phone this weekend. The leaders of France and Germany, who were also present during talks earlier this week, will also participate in the calls.

The UN Security Council is expected to meet on Sunday for emergency talks.

Additional reporting by Press Association