UPDATE 1-Russia blames Nusra Front for wrecking planned truce in Syria's Aleppo

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MOSCOW, May 4 (Reuters) - The Russian Defence Ministry on Wednesday said an upsurge in violence by Nusra Front militants had thwarted plans to extend a truce to the Syrian city of Aleppo the previous day, Russian news agencies reported.

Russian Foreign Minister Sergei Lavrov suggested on Tuesday after meeting U.N. Syria envoy Staffan de Mistura that a deal covering Aleppo was close, saying Russian and U.S. military personnel might announce a decision “in the coming hours”.

But such a local truce, also known as “a regime of calm,” never materialised.

“As a result of attacks by the Nusra Front on the Az Zagra quarters, and heavy shelling by Hellfire rocket systems of other residential areas which caused numerous deaths among civilians, the introduction of a ‘regime of calm’ in Aleppo was disrupted,” Russian news agencies quoted Russian Defence Ministry spokesman Igor Konashenkov as saying on Wednesday.

Aleppo has been the scene of the worst surge in fighting in recent days, wrecking the first major ceasefire of the five-year-old civil war, sponsored by the United States and Russia, which had held since February.

Russia and U.S. military officers were now holding “active consultations” with Syria’s government leadership and the “moderate opposition” on how to introduce a “regime of calm” in Aleppo as soon as possible, Konashenkov said.

The ceasefire in Aleppo and its suburbs was originally planned to last for 24 hours and to be later extended for a further two days, he was cited as saying.

Rebel fighters launched an assault in Aleppo on Tuesday, firing rockets on a hospital.

The Syrian Observatory for Human Rights, a British-based group that monitors the conflict, said rebel rockets had killed 19 people in government-held territory, including an unspecified number at the al-Dabit hospital. (Reporting by Lidia Kelly; Writing by Dmitry Solovyov; Editing by Andrew Osborn)