The government of South Sudan insisted on Friday it was playing an impartial role in efforts to end the fighting in Sudan after Khartoum protested over its hosting of a Rapid Support Forces envoy.
South Sudan, which won independence from Sudan in 2011, has been playing a mediation role through the regional bloc IGAD to try to resolve the conflict between the paramilitary RSF and army chief Abdel Fattah al-Burhan's forces.
Sudan's foreign ministry said in a statement published Thursday that it had issued an "official protest memorandum" to Juba to express its "strong denunciation" over a visit this week by one of RSF leader Mohamed Hamdan Daglo's advisers.
Daglo's envoy Yusif Isha held talks with South Sudanese President Salva Kiir and IGAD officials in Juba on Wednesday and later told a press conference the RSF was "ready to take part in any step taken by him (Kiir) to reach a lasting peace in Sudan."
Kiir has held several conversations with Sudan's de-facto leader Burhan and his deputy-turned-rival Daglo, and also hosted a Burhan envoy in Juba on May 8.
South Sudan's government "has continued to play its part within IGAD with absolute impartiality," the foreign ministry said in a statement on Friday.
"The notion of mediation entails engagement of all parties with equal measure," it added.
Since the conflict erupted in Khartoum in mid-April, around 1,000 people have been killed and fighting is raging despite several ceasefire deals.
The United Nations has warned it expects more than one million people to flee to neighbouring countries this year, and Juba said Friday that over 60,000 have so far crossed into South Sudan.