JUBA, Sudan (Reuters) - Militia fighters attacked the capital of south Sudan's oil-producing Upper Nile state on Saturday, the southern army said, causing an unknown number of casualties.
"There is fighting going on in Malakal. Militia have penetrated the town. They raided at night," said southern army spokesman Philip Aguer.
The attack on a state capital marked an escalation in a wave of clashes between the south's army and militias which has aroused fears over the stability of south Sudan in the countdown to its secession, due to take place on July 9.
Aguer blamed the attack on a militia he said was aligned with renegade leader George Athor, a former army officer who rebelled last year saying he had been cheated out of the governorship of neighboring Jonglei state in elections.
In January, southerners overwhelmingly voted to declare independence in a referendum promised in a 2005 peace deal that ended decades of civil war with the south.
(Reporting by Jeremy Clarke, writing by Andrew Heavens; editing by Andrew Dobbie)