TOP WRAP 3-Biden says Russia is considering using chemical, biological weapons in Ukraine

(Updates with comment from China, Pakistan, paragraph 18)

* Ukrainian generals expect more indiscriminate bombing

* Ukraine says "No question of surrender" in Mariupol

* Holocaust survivor killed in shelling

By Pavel Polityuk and James Mackenzie

MARIUPOL/LVIV/KYIV, Ukraine, March 22 (Reuters) - Ukraine's military warned the public on Tuesday of more indiscriminate Russian shelling of critical infrastructure as U.S. President Joe Biden issued one of his strongest warnings yet that Russia is considering using chemical weapons.

Russian troops have failed to capture any major Ukrainian city more than four weeks into their invasion, and increasingly are resorting to massive destruction of residential areas with air strikes, long-range missiles and artillery.

The southern port of Mariupol has become a focal point of Russia's assault and is largely in ruins with bodies on the streets but attacks were also reported to have intensified on the second city of Kharkiv on Monday.

Russian forces were expected to continue to attack critical infrastructure with "high-precision weapons and indiscriminate munitions”, Ukraine's armed forces said in a statement.

Biden, without citing evidence, said Russia's false accusations that Ukraine had biological and chemical weapons illustrated that President Vladimir Putin's "back was against the wall" and he was considering using such weapons.

"Now he's talking about new false flags he's setting up including, asserting that we in America have biological as well as chemical weapons in Europe, simply not true," Biden said at a business event.

"They are also suggesting that Ukraine has biological and chemical weapons in Ukraine. That's a clear sign he's considering using both of those."

The Russian embassy in Washington did not immediately respond to a request for comment.

Biden also told businesses to be alert for cyber attacks by Russia. "It's part of Russia's playbook," he said in a statement.

The United States and its allies have previously accused Russia of spreading an unproven claim that Ukraine had a biological weapons programme as a possible prelude to using such weapons but Biden's remarks on Monday were some of his strongest on the subject.

Russia says it does not attack civilians although the devastation wrought on Ukrainian towns such as Mariupol and Kharkiv are reminiscent of previous Russian assaults on cities in Chechnya and Syria.

Putin calls the war, the biggest attack on a European state since World War Two, a "special military operation" to disarm Ukraine and protect it from "Nazis". The West calls that a false pretext for an unprovoked war of aggression.