Ukraine president Volodymyr Zelenskiy has said new sanctions by the west against Russia do not go far enough and will be seen by invading forces as a “permission to attack”, as fears of an assault on the east of the country intensify.

It comes after the US, UK and EU unveiled a raft of new sanctions targeting Russian banks and the country’s elites. The US measures include a ban on investing in Russia as well as sanctions on president Vladimir Putin’s adult daughters. The EU sanctions include a ban on coal imports and restrictions on banks.

“This package has a spectacular look. But this is not enough,” Zelenskiy said in his nightly address.

“If there is no really painful package of sanctions against Russia and if there is no supply of weapons … it will be considered by Russia as a permission. A permission to attack,” he said, calling for the west to reject Russian oil and completely block the country’s banks from the international finance system.

Zelenskiy also said, without providing evidence, that Russian troops were now trying to cover up atrocities in Ukraine. Grisly images of dead civilians in the streets of Bucha this week sparked international condemnation and calls for Russian forces to be tried for war crimes.

The UN general assembly will vote on Thursday on whether to suspend Russia from the UN premier human rights body in the wake of the discoveries. Russia has denied responsibility and suggested the images were fake or the deaths occurred after its troops pulled out. However, satellite images show that bodies were lying on streets in Bucha for days before Russian troops left the town.

“Russia’s participation on the Human Rights Council is a farce,” US ambassador Linda Thomas-Greenfield said this week.

Ahead of an expected Russian military assault in the coming days, Ukraine has urged civilians to leave the east of the country “while the opportunity still exists”.

The deputy prime minister, Iryna Vereshchuk, said the authorities would “not be able to help” residents who stayed behind once large-scale fighting erupted. She said the governors of the Kharkiv, Luhansk and Donetsk regions were calling on people to move immediately to safer areas. “It has to be done now, because later people will be under fire and face the threat of death. There is nothing they will be able to do about it,” she posted on Telegram.

The deputy prime minister emphasised: “It is necessary to evacuate as long as this possibility exists. For now, it still exists.”

The Kremlin has said it intends to seize the entire Donetsk region, amid reports that Putin is keen to declare victory in Ukraine in time for 9 May, the annual commemoration of the Soviet defeat of Hitler in the second world war.

One western official said Putin would want to have an “announceable success” by then, which could create “some tension” with Russian commanders as exhausted forces were likely to be thrown into battle fairly soon in an attempt to gain ground in the east.

The new focus on the east follows the humiliating failure of Putin’s original apparent plan to seize the capital, Kyiv, overthrow the Zelenskiy government and subjugate most of Ukraine in a matter of days or weeks.

Instead, Russian troops who advanced on Kyiv were forced to withdraw to Belarus after shattering losses. The Kremlin has also pulled its forces out of the Sumy region after its advance there became bogged down.

According to revised estimates, 29 of Russia’s battalion tactical groups – the smallest operating unit of its forces – are now “combat non-effective”, from an invading force estimated to be at about 125 battalions, which comprises around 75% of Russia’s total army.