WARSAW/KYIV (Reuters) - Ukraine will retaliate after a Russian missile strike killed at least 29 people and damaged a children's hospital in Kyiv, President Volodymyr Zelenskiy said on Monday during a visit to Warsaw during which he signed a security pact with Poland.

As world leaders prepare to head to a NATO summit which starts on Tuesday in Washington, Zelenskiy called on Kyiv's allies to give a firm response to Monday's attack in a press conference that started with a minute's silence for the victims.

"I would also like to hear from our partners (about) a greater resilience and a strong response to the blow that Russia has once again dealt to our people, to our land, to our children," he said.

"We will retaliate against these people, we will deliver a powerful response from our side to Russia, for sure. The question to our partners is: can they respond?"

Zelenskiy said Kyiv wanted to be able to use weapons supplied by its partners to hit the sites in Russia that attacks were being launched from.

"I think, we would really like to receive such decision from our partners," he said. "Or they would like to see the strikes again."

Zelenskiy said Ukraine was waiting for concrete steps from its Western partners to strengthen its air defences and protect its energy sector.

He said Kyiv was initiating an emergency meeting of the UN Security Council in connection with the Russian attack.

Polish Prime Minister Donald Tusk said that Poland was discussing how it could help provide energy for Ukraine before the winter as Russia targets Ukrainian energy infrastructure.

He also said that Poland was open to the idea of shooting down Russian missiles that were heading for NATO territory while they were still over Ukrainian soil.

"We need clear cooperation within NATO here, because such actions require such joint NATO responsibility... we are open to it, logic indicates it that this would absolutely be a more effective action," he said.

The agreement with Poland was the 21st such pact Kyiv has signed with countries including the United States, Britain, France and Germany.

Officials have previously said the agreements are not the same as the mutual defence pact between NATO nations, but are pledges to provide Ukraine with weapons and other aid to bolster its own security and deter any future invasion.

(Reporting by Barbara Erling, Anastasiia Malenko, Yuliia Dysa, Olena Harmash, Anna Wlodarczak Semczuk, Anna Koper, writing by Alan Charlish; Editing by Bernadette Baum, William Maclean)