Major humanitarian organisations have pledged to continue to work in war-torn South Sudan despite a string of attacks and kidnappings targetting aid workers.

The South Sudan conflict, which erupted in 2013, has killed thousands and displaced millions. It has also resulted in famine and a mass exodus of refugees dubbed "Africa's worst refugee crisis."

Millions across the country are in urgent need of life-saving assistance and the world's biggest aid agencies have been active in South Sudan for some years.

But as law and order in the country breaks down, aid workers have increasingly been targeted in kidnappings, killings and sexual assaults.

Earlier this week seven members of NGO Grassroots Empowerment and Development Organisation (Gredo) were ambushed and killed.

And although the incident was described as the worst attack on NGO staff since the war broke out, it was only the latest example of violence against aid agency workers.

The UN has estimated that at least 79 aid workers have been killed in South Sudan since the war began. Of these, 12 have been killed since the beginning of 2017.

Earlier in March, eight members of the US charity Samaritan's Purse were abducted from the Mayendit village. It was claimed that rebels demanded aid deliveries as a ransom, but the workers were later released.

One of the worst outbreaks of violence against aid workers occurred in the capital Juba in July 2016, when hundreds of people were killed during three days of heavy fighting between warring sides.

Government troops were accused of killing at least one journalist, while a number of aid workers who stayed at a compound near Juba were raped, beaten, and subjected to mock executions.

The UN peacekeeping mission in South Sudan (Unmiss) and several embassies were accused of failing to protect civilians and aid workers. Later that year, a UN probe concluded Unmiss had failed to protect people due to "a lack of leadership on the part of key senior mission personnel".

But the work of aid agencies in South Sudan is also hindered by bureaucratic impediments.

Last year, the government was criticised after parliament passed a Non-Governmental Organisations bill that limited foreign-aid workers in the country. According to the law, no more than a fifth of current foreign aid worker numbers would be allowed to work in the country and at least 80% of the staff employed by NGOs would have to be South Sudanese.

South Sudan also faced a backlash from aid agencies for its recent decision to charge aid workers $10,000 for visas.

A total of 137 aid organisations, including 62 national NGOs, 63 international NGOs and 12 UN entities are taking part in the 2017 UN Office for the Coordination of Humanitarian Affairs Humanitarian Response Plan in South Sudan.

No humanitarian organisation has so far hinted they are planning to withdraw staff in spite of the deteriorating security in the African nation.

A spokesperson for the UN children charity (Unicef) told IBTimes UK: "Unicef's operations in South Sudan are continuing as usual and we are not considering to withdraw staff."

Unmiss also intends to continue with its operations. "While the incident over the weekend is a tragic and senseless act of violence, the UN is not withdrawing staff from its operations. The mission will continue to support the people of South Sudan," a spokesperson told IBTimes UK.

But others acknowledged that South Sudan has become one of the most difficult countries to operate in at the moment.

"The conflict in South Sudan, coupled with attacks on aid workers and deliberate restrictions of humanitarian access is exacerbating the deadly impact of famine on millions of people. Without vital assistance, famine and malnutrition will spread across South Sudan and more people will die," Priti Patel, secretary of UK government's Department of International Development (Dfid) said.

Fears are increasing that killings, assaults and kidnappings could hinder, or at the very least delay, humanitarian assistance in the country.

Ultimately, this will harm vulnerable civilians, particularly those in Unity state, where at least 100,000 people are facing famine. Aid deliveries that could save lives will also be delayed by the arrival of the rainy season, which will make some roads inaccessible.

As a result, the refugee influx will further increase, posing difficult challenges to hosting countries, some of which are also experiencing lack of food due to a drought.