File photo taken on Nov.16, 2015, shows refugee children playing games at a refugee camp in Juba, South Sudan. (Xinhua/Pan Siwei)

JUBA, July 9 (Xinhua) -- The UN Children's Fund (UNICEF) on Monday called on South Sudan warring parties to the conflict to intensify efforts to bring a lasting peace in the country.

UNICEF said that conflict and underdevelopment have beset South Sudan for decades, leaving its children out of school, malnourished and vulnerable to disease, abuse and exploitation.

"Warring parties can and must do more to bring back peace. The children of South Sudan deserve better," said Henrietta H. Fore, UNICEF's Executive Director, said in a statement issued in Juba as the country marks 7th independent anniversary.

According to UNICEF, out of 3.4 million babies born in South Sudan since it became the world's youngest country in 2011, 2.6 million have been born in war.

"The prospect of a better future following the country's independence in 2011 was short-lived following the eruption of a civil war in 2013," it said.

For the third year in a row, South Sudan is marking its Independence Day without any celebrations due to financial difficulties facing the country.

The government said on Friday it was cancelling official celebrations of the 7th anniversary due to the economic hardship and political instability the country is facing.

However, some South Sudanese organized small parties to celebrate with friends on Monday, while others can hardly afford the expenses.

UNICEF said the conflict has also pushed hundreds of thousands of children out of school, with 1 in 3 schools damaged, destroyed, occupied or closed since 2013.

It said the country now has the highest proportion of out-of-school children in the world as over 2 million children of those who should be attending classes are not receiving an education.

Fore said the signing of a permanent ceasefire between the two main warring parties in Khartoum last month was a positive step in what has been a faltering peace process.

"We now count on the leadership and commanders to respect it while ensuring that aid workers are given unrestricted access to those in need," she said.

"South Sudan was the first country I visited when I became Executive Director and I saw for myself how harmed children have been by the war. They simply cannot endure anymore."

More than 100 aid workers have been killed in the violence since the conflict began in 2013, including a driver for UNICEF just last week.

According to UNICEF, although 800 children have been released from armed groups since the beginning of the year, an estimated 19,000 children continue to serve as fighters, cooks, porters and messengers and to suffer sexual abuse - up from 500 when the conflict first broke out in 2013.