KYIV, Ukraine — Russian missiles hit Ukraine’s Black Sea port of Odessa just hours after Moscow and Kyiv signed deals to allow grain exports to resume from there. Ukraine’s Foreign Ministry denounced Saturday’s airstrikes as “spit in the face” of Turkey and the United Nations, which brokered the agreements.

Two Russian Kalibr cruise missiles hit the port’s infrastructure and Ukrainian air defenses brought down two others, the Ukrainian military’s Southern Command said. It didn’t specify the damage or say if the strike caused casualties.

“It took less than 24 hours for Russia to launch a missile attack on Odessa’s port, breaking its promises and undermining its commitments before the UN and Turkey under the Istanbul agreement,” the Ukrainian Foreign Ministry spokesman, Oleg Nikolenko, said. “In case of non-fulfillment, Russia will bear full responsibility for a global food crisis.”

Mr. Nikolenko described the missile strike on the 150th day of Russia’s war in Ukraine as President Putin’s “spit in the face of U.N. Secretary-General Antonio Guterres and Turkish President Recep Tayyip Erdogan, who made great efforts to reach agreement.”

Mr. Guterres’s office said the UN chief “unequivocally condemns” the strikes.

“Yesterday, all parties made clear commitments on the global stage to ensure the safe movement of Ukrainian grain and related products to global markets,” the Guterres statement said. “These products are desperately needed to address the global food crisis and ease the suffering of millions of people in need around the globe. Full implementation by the Russian Federation, Ukraine and Turkey is imperative.”

During a Friday signing ceremony at Istanbul, Mr. Guterres hailed the deals to open Ukraine’s ports in Odessa, Chernomorsk, and Yuzhny to commercial food exports as “a beacon of hope, a beacon of possibility, a beacon of relief in a world that needs it more than ever.”

The agreements sought to clear the way for the shipment of millions of tons of Ukrainian grain and some Russian exports of grain and fertilizer that have been blocked by the war. Ukraine is one of the world’s largest exporters of wheat, corn, and sunflower oil, but Russia’s invasion of the country and naval blockade of its ports halted shipments.

Documents obtained by the Associated Press showed the deals called for the creation of a UN-led joint coordination center in Istanbul where officials from Ukraine, Russia, and Turkey would oversee the scheduling and searches of cargo ships.

President Zelensky said in his nightly video address that the agreements offered “a chance to prevent a global catastrophe — a famine that could lead to political chaos in many countries of the world, in particular in the countries that help us.”

The head of Mr. Zelensky’s office, Andriy Yermak, said on Twitter that the Odessa strike coming so soon after the endorsement of the Black Sea ports deal illustrated “the Russian diplomatic dichotomy.”

The American ambassador to Ukraine, Bridget Brink, denounced the Russian strike on the port of Odessa as “outrageous.” “The Kremlin continues to weaponize food,” she tweeted. “Russia must be held to account.”

Along with the strike on Odessa, Russia’s military fired a barrage of missiles Saturday at an airfield and a railway facility in central Ukraine, killing at least three people, while Ukrainian forces launched rocket strikes on river crossings in a Russian-occupied southern region.

The attacks on key infrastructure marked new attempts by the warring parties to tip the scales of the grinding conflict in their favor.

In Ukraine’s central Kirovohradska region, 13 Russian missiles struck an airfield and a railway facility. Governor Andriy Raikovych said at least one serviceman and two guards were killed and another 16 people were wounded in the strikes near the city of Kirovohrad.

In the southern Kherson region, which Russian troops seized early in the invasion, Ukrainian forces preparing for a potential counter offensive fired rockets at Dnieper River crossings to try to disrupt supplies to the Russians. Still, Russian troops have largely held their ground in the Kherson region just north of the Crimean Peninsula, which Russia annexed in 2014.

Fighting raged unabated in eastern Ukraine’s industrial heartland of the Donbas, where Russian forces tried to make new gains in the face of stiff Ukrainian resistance.

Earlier this week, the Ukrainians bombarded the Antonivskyi Bridge across the Dnieper River using the U.S.-supplied High Mobility Artillery Rocket System, the deputy head of the Russia-appointed regional administration in Kherson, Kirill Stremousov, said.

Mr. Stremousov told Russian state news agency Tass that the only other crossing of the Dnieper, the dam of the Kakhovka hydroelectric plant, also came under attack from rockets launched with the weapons supplied by Washington but wasn’t damaged.

HIMARS, which can fire GPS-guided rockets at targets 50 miles away, out of reach of most Russian artillery systems, have significantly bolstered the Ukrainian strike capability.

In addition, Ukrainian forces shelled an automobile bridge across the Inhulets River in the village of Darivka, Mr. Stremousov told Tass. He said the bridge just east of the regional capital of Kherson sustained seven hits but remained open. Mr. Stremousov said that unlike the Antonivskyi Bridge, the small bridge in Darivka has no strategic value.

Since April, the Kremlin has concentrated on capturing the Donbas, a mostly Russian-speaking region of eastern Ukraine where pro-Russia separatists have proclaimed independence.

However, the Russian foreign minister, Sergey Lavrov, emphasized Wednesday that Moscow plans to retain control of other areas in Ukraine that its forces have occupied during the war.

By Susie Blann