KYIV: A series of blasts was heard to the west of the Ukrainian capital Kyiv's centre on Sunday, minutes after air raid sirens sounded, a Reuters correspondent reported.

Ukrainian media reported explosions and a gunfight in a nearby town.

According to Ukrainian news website Segodnya.ua, a bridge has been blown up near the town of Bucha west of Kyiv.

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It was unclear whether it had been bombed by Russian troops or destroyed by the Ukrainian side.

Anton Herashchenko, an advisor to Ukraine's interior minister, said fighting was under way in Bucha with Russian forces that were trying to advance towards Kyiv.