JUBA, March 29 (Xinhua) -- South Sudan's cease-fire monitors on Thursday expressed deep concern regarding ongoing reports and allegations of hostilities in the southern area of Central Equatoria and areas of Upper Nile.

The Ceasefire Transitional Security Arrangement Monitoring Mechanism (CTSAMM) urged warring parties of their obligations to cease all hostilities and adhere to the provisions of the Agreement of the Cessation of Hostilities (ACOH), including freezing of forces and military movements without prior authority of CTSAMM.

"The 61st Extra-Ordinary Session of IGAD Council of Ministers underscored its resolve to bring any violators of ACOH and spoilers of the peace process to account," it said in a statement issued in Juba, urging all parties to commit to implement the agreement in full and in good faith.

The South Sudanese government and the 14 rebel groups agreed in December last year to the cease-fire agreement and release of political prisoners but the agreement broke down within 48 hours amid continued intermittent clashes further displacing civilians.

The CTSAMM reiterated its mandate to freely monitor the implementation of the cease-fire deal as outlined in the agreement.

It added that it continues to monitor these developments and will send monitoring and verification teams (MVTs) to the areas affected as soon as is possible in order to ascertain whether any violation of the ACOH has taken place.

The CTSAMM further stressed that any violation is unacceptable and will be referred to the IGAD Council of Ministers and JMEC.

"The CTSAMM calls on all parties to immediately cease all hostilities, and to investigate and ensure accountability of any breach of the ACOH. Where MVTs are required to conduct investigations, parties are reminded of their obligation to guarantee free movement and unhindered access," it said.

South Sudan descended into violence in December 2013 after President Salva Kiir sacked his former deputy Riek Machar leading to fighting between mostly Dinka ethnic soldiers loyal to Kiir and ethnic Nuer soldiers loyal to Machar.