United Nations Secretary-General Antonio Guterres has landed in Somalia on what he calls an emergency visit to focus on famine.

The U.N. chief announced his Tuesday morning arrival in the Horn of Africa nation on Twitter, saying that “people are dying. The world must act now to stop this.”

Somalia is part of a massive $4 billion aid appeal launched last month for four nations suffering from conflict and hunger. The others are Nigeria, Yemen and South Sudan, where famine already has been declared.

Somalia over the weekend announced its first death toll since declaring a national disaster last week, saying 110 people had died in a 48-hour period in a single region.

The United Nations estimates that 5 million people in Somalia need aid, amid warnings of a famine.