The Russian military carried out overnight missile strikes on the southern region of Odesa, Ukrainian officials said Saturday, injuring four people and damaging port infrastructure as part of a broader effort to strangle the Ukrainian economy.

The Ukrainian southern military command said Russia had used supersonic cruise missiles that hit a boardinghouse and a granary in the second attack on the area in two days as Moscow continued to target its ports and grain facilities.

Ukraine has been among the world’s biggest exporters of grain and a major supplier to parts of Africa and the Middle East. After Russia’s blockade of the Black Sea this summer, those exports plummeted, worsening global shortages and raising fears of famine, but Ukraine since has devised alternative routes, trying to protect a crucial source of income during the war.

Missile debris and the blast wave from the strikes also caused a fire in a garage and damaged several apartment buildings, the Ukrainian military said in a post on the Telegram messaging app, which included photographs of smashed windows and collapsed building walls. The injuries were caused by broken glass, according to Oleh Kiper, the head of the Odesa region’s military administration.

Ukrainian officials did not specify which areas were hit, but local Ukrainian news media reported that strikes landed in the port city of Chornomorsk, just outside Odesa. The Russian military did not immediately comment on the strikes.

Moscow pulled out of a deal in July that had allowed for the safe passage of Ukrainian grain through the Black Sea during the war, and since then, Russian forces have struck Ukraine’s ports with missiles and drones in an attempt to squeeze its trade with the rest of the world.

Odesa, home to the country’s busiest ports, has been particularly hard hit, with extensive damage to its infrastructure. A day earlier, Russian drones hit a grain silo near the port city of Izmail, also in the Odesa region. Nine trucks caught fire at the site, Kiper wrote on Telegram.

To get exports of grain and other goods moving again, Ukraine established an alternative corridor that calls for ships to hug the western coast of the Black Sea, providing some degree of security by moving in the territorial waters of Romania, Bulgaria and Turkey, all NATO members.