“Ibrahimovic has sustained an injury to his right soleus muscle during yesterday’s training session,” the Serie A team said in a statement.
“The Achilles tendon is perfectly intact. The player will undergo a scan in 10 days time.”
Milan did not say for how long the 38-year-old would be out of action, although Italian media reports say he could be facing four weeks on the sidelines, as Serie A eyes a potential restart next month.
Ibrahimovic rejoined the seven-time European champions during this season’s winter transfer window. He suffered a calf injury shortly after signing in January.
He returned to Italy two weeks ago from Sweden, where he had been training with Hammarby, in order to prepare for a possible return to action.