JUBA, South Sudan, July 10 (UPI) -- Gunfire from "heavy weaponry" was reported outside a United Nations building in the South Sudan capital of Juba Sunday morning, a city racked with violence over the past week as the country marked its fifth year of independence.
The U.N. Mission to South Sudan sent out a series of tweets describing a "heavily armed exchange" outside the compound, CNN reported.
Forces loyal to South Sudan Vice President Riek Machar said they have been attacked by government troops. Col. William Gatjiath, Machar's military spokesman, said President Salva Kiir "isn't serious" about a peace agreement, BBC reported.
A spokesman for the vice president said South Sudan is "back to war."
A gun fight broke out over the weekend when Kiir and Machar met to discuss previous clashes between their armed factions.
A number of groups tweeted their condemnation over the renewed violence, including UNICEF which has been working to find family for children displaced by the violence.
Up to 150 people were reported killed in the gun fights Friday before calm was restored Saturday.
Gatjiath said "hundreds" of Machar's troops were killed Sunday and that troops loyal to the vice president were advancing on Juba.
Locals told Al Jazeera the airport in Juba had shut down and Kenya Airline tweeted that it was suspending flights to the city due to "uncertain security situation."