Rescue workers in the southern Ukrainian city of Odesa pulled the bodies of a mother and baby from the rubble of an apartment building on Sunday, as the death toll in a Russian attack two days earlier rose to 12. President Volodymyr Zelensky of Ukraine said delays by allies in supplying air defenses had contributed to the deaths.

The denunciation by Mr. Zelensky appeared to reflect frustration that Ukraine’s capacity to resist Moscow’s military campaign and protect its own citizens has been undermined by the failure of the U.S. House of Representatives to pass a multibillion-dollar military aid package.

A drone hit the building overnight on Friday, and since then emergency workers have been picking through its rubble. Odesa, a port city on the Black Sea, was a key initial target of Moscow’s full-scale invasion two years ago, and in recent months Russian forces have frequently targeted it with drone strikes, often launched from Crimea. This weekend’s attack, however, has caused particular outrage among Ukrainians.

Rescue workers said that the woman and baby were found together. “The mother tried to cover her 8-month-old child,” said a statement by the State Emergency Service posted on the Telegram social messaging service. “They were found in a tight embrace.”

The bodies of a 10-year-old boy and his 8-year-old sister were later found in the debris, the head of the regional military administration, Oleh Kiper, said on Telegram, bringing the death toll to 12. “Unspeakable, terrible grief for Odesa and all of Ukraine,” he said.

A 3-year-old girl was among eight people who had been wounded, Mr. Zelensky said in an overnight speech, in which he said that Ukrainian civilians had become more vulnerable because the country’s armed forces lacked air defenses that could shoot down the Shahed drones that Iran has supplied to Moscow.

“The world has enough missile defense systems, systems to protect against Shahed drones and missiles. And delaying the supply of weapons to Ukraine, missile defense systems to protect our people, leads, unfortunately, to such losses,” he said. He did not refer specifically to U.S. aid, but the country is by far Ukraine’s biggest overall military donor.

“When lives are lost, and partners are simply playing internal political games or disputes that limit our defense, it’s impossible to understand. It’s unacceptable,” Mr. Zelensky said.

More than 10,000 Ukrainian civilians have been killed and more than 18,000 wounded in the last two years, according to U.N. data, the vast majority by explosions rather than gunfire. In a further attack, two people were critically wounded and 14 others were hurt on Sunday in a Russian strike on Kurakhove, a small city around 10 miles west of the front line in the Donetsk region, according to the head of the regional military administration, Vadym Filashkin.

For many Ukrainians, air-raid alerts have become a fact of life and the country has come to rely on air defenses supplied by the United States and other NATO allies.

But a U.S. bill that includes $60.1 billion in military aid for the government in Kyiv, including for air defenses, has for months languished in the House, stalled by opposition from some Republicans and from former President Donald J. Trump, who is the likely Republican nominee for president.

Since the full-scale invasion began, Mr. Zelensky has repeatedly pressed Ukraine’s allies for more weaponry, often using strong language that at times has irked some leaders in NATO countries. He has argued that Ukraine’s defense against Moscow is central to all of Europe’s security as well as to democratic values more broadly.

Ukrainian military commanders have also said that a lack of ammunition and artillery have made it harder to resist Russian battlefield advances, not least around the city of Avdiivka in the eastern Donetsk region, which fell to Russian forces last month.

Ukraine’s counteroffensive, which began last June, failed to achieve its objectives, and since then Moscow has gradually regained the initiative in the war, taking small chunks of territory amid intense fighting. Military experts say that Ukraine could face a difficult year on the battlefield, particularly if a lack of military aid forces it to ration ammunition severely.