LVIV, Ukraine (AP) — Ukrainian President Volodymyr Zelenskyy said Sunday that Russian troops in southern Ukraine have been carrying out torture and kidnappings, and he called on the world to respond.

“Torture chambers are built there,” Zelenskyy said in an evening address to the nation. “They abduct representatives of local governments and anyone deemed visible to local communities.”

Zelenskyy said humanitarian aid has been stolen, creating famine.

In occupied parts of the Kherson and Zaporizhzhia regions, he said, the Russians are creating separatist states and introducing Russian currency, the ruble.

Intensified Russian shelling of Ukraine’s second-largest city, Kharkiv, has killed 18 people and wounded 106 in the last four days alone, Zelenskyy said.

“This is nothing but deliberate terror. Mortars, artillery against ordinary residential neighborhoods, against ordinary civilians,” he said.

He said a planned Russian offensive in eastern Ukraine “will begin in the near future.”

Zelenskyy again called for increased sanctions against Russia, including its entire banking sector and oil industry.

“Everyone in Europe and America already sees Russia openly using energy to destabilize Western societies,” Zelenskyy said. “All of this requires greater speed from Western countries in preparing a new, powerful package of sanctions.”

The long battered city of Mariupol appeared on the brink of falling to Russian forces Sunday after eight weeks under siege, a new development that would give Moscow crucial success in Ukraine after failed attempts to capture key cities.

The Russian military estimated that about 2,500 Ukrainian fighters are holding out at a hulking steel plant with a warren of underground passageways provided the last pocket of resistance in Mariupol. Russia gave another deadline for their surrender, saying those who put down their weapons were “guaranteed to keep their lives,” but the Ukrainian defenders continued to fight back.

“All those who will continue resistance will be destroyed,” Maj. Gen. Igor Konashenkov, the Russian Defense Ministry’s spokesman, said. He said intercepted communications indicated there were about 400 foreign mercenaries along with the Ukrainian troops at the Azovstal steel mill, a claim that couldn’t be independently verified.