JUBA, South Sudan -- The number of South Sudanese refugees in East Africa could pass 1 million this year, the United Nations refugee agency said Friday, calling on armed groups to allow safe passage for people fleeing the latest fighting.

There is concern about fresh outflows of refugees following military clashes in recent days in the capital, Juba, said Ann Encontre, a UN refugee co-ordinator in South Sudan. She appealed for $701 million in relief aid.

"They are supposed to be the generation of tomorrow, the generation that will lead and rebuild their country, but right now, they are suffering enormously," she said. "They have been deprived of a normal life."

Even before the resurgence of violence in the past week, hundreds of thousands of refugees had been sheltering in Uganda, Sudan, Ethiopia and elsewhere since civil war began in December 2013.

But there are new reports that South Sudan authorities are blocking some citizens, including those with U.S. or Canadian dual nationality, from leaving the country.

Opposing army factions have clashed in Juba over the past week, with forces backing President Salva Kiir pushing many opposition forces out of their bases in the city and bombing the home of former rebel leader Riek Machar, who is now the country's first vice-president.

The fighting has threatened a peace deal reached in August to end the civil war between supporters of Kiir and Machar that left tens of thousands dead. The deal called for a transitional government that included members of both sides.

Both Kiir and Machar on Monday called for a cease-fire, which has appeared to hold.

But the UN has said more than 40,000 fled their homes in the latest fighting to seek shelter at U.N. and other sites in Juba.