Four weeks since fierce fighting broke out in the southern Philippines, some who fled the battle are dying in overcrowded and unsanitary evacuation centers, health officials say.

At least 19 people have died in the centers since fighting between security forces and Islamist militants erupted in the city of Marawi, said Alinader Minalang, the health director for the Lanao del Sur province.

Three hundred cases of diarrhea have been recorded among the nearly 40,000 people huddled in emergency shelters set up in community halls, gymnasiums and Islamic schools, he said.