By Omer Berberoglu

KYIV (Reuters) -Russian air strikes and shelling hit Kyiv on Tuesday killing at least four people, authorities said, as invading forces tightened their grip on the Ukrainian capital and the mayor announced a 35-hour curfew starting at 8 p.m. (1800 GMT).

Two large blasts echoed across the centre of the city just before dawn on Tuesday. Late on Monday, tracer bullets flashed across the night sky as Ukrainian forces apparently targeted an enemy drone.

“Today is a difficult and dangerous moment,” mayor Vitali Klitschko said.

“The capital is the heart of Ukraine, and it will be defended. Kyiv, which is currently the symbol and forward operating base of Europe’s freedom and security, will not be given up by us.”

He called on men who took wives and children to the relative safety of the west of the country earlier in the conflict to return to the capital to fight. Some have done so already, he and his brother Wladimir told Reuters in a recent interview.

Reuters witnesses saw a high-rise apartment block in flames after being struck by artillery. Firefighters tried to douse the blaze and rescue workers helped evacuate residents trapped inside using mobile ladders. A body lay on the ground in a bag.

The Artem weapons factory in central Kyiv was also hit, with footage taken by a local resident showing smoke coming from the roof. Outside kiosks nearby, shopkeepers and helpers swept up glass and other debris from the impact of the explosions.

Russia said on Monday that it planned to attack Ukrainian arms factories in retaliation for what it said was a Ukrainian strike on the separatist-controlled city of Donetsk, and urged workers and local residents to stay away. Ukraine denied launching an attack.

Kyiv has been spared the worst of the fighting since Russia invaded Ukraine on Feb. 24, but the Russian military is slowly closing in on the city and the shelling has intensified.

“What is happening right now in Kharkiv, in Mariupol and other cities – it was understandable that sooner or later it would happen in Kyiv,” said local resident Igor Krupa.

Sitting on the ground outside the badly damaged apartment building, he described how he had cocooned himself with furniture and metal weights before going to sleep.

“This actually saved me because all the windows went out and all the debris went into the apartment, and I remained unwounded. Just a couple of scratches.”

In another part of the city, residents cleared debris from their homes after shelling blew out windows, ruined balconies and left wreckage strewn across the ground.

Thousands of people have been killed in the conflict and millions more displaced.

Russia, which denies targeting civilians, calls its actions a “special military operation” to “denazify” the country, a claim that Ukraine and its allies reject as a pretext for an unjustified and illegal attack.

(Writing by Mike Collett-White; Editing by Janet Lawrence)

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