Senior South Sudan leader says Khartoum is involved in arming, financing and training militias in the South [AFP]

South Sudan has announced it will suspend talks with Khartoum about its planned secession in July after accusing Omar al-Bashir, the Sudanese president, of plotting to overthrow the new government in the south.

Pagan Amum Okiech, secretary-general of Sudan Peoples Liberation Movement (SPLM), told Al Jazeera on Saturday that the south would suspend talks with Bashir's ruling National Congress Party (NCP) about plans for the secession.

“The ruling National Congress Party [NCP] of Sudan is recruiting, arming, financing and deploying militias in South Sudan with the aim to destabilise the South,” he said.

 “We have detailed information and documents showing the NCP and various institutions of government like military intelligence in Khartoum, so-called peace advisory council and or national security involved in arming, financing and training militias in South Sudan."

However, Rabie Abdelati, senior ruling party official in north, told the Reuters news agency on Saturday that the accusation of a northern plot was "ridiculous".

Wave of clashes

The news followed reports of the death of at least 23 people in an attack on Saturday in Malakal, one of the south's three main settlements, marking an escalation in a wave of clashes between the south's army and rebel fighters.

The fighting is still taking place in the oil-producing town and has raised fears over the stability of the region in the countdown to its secession - due on July 9.

George Athor, southern militia leader, told Reuters one of his deputies had launched the assault to seize weapons and to strike back after a series of army offensives against his men.

Athor is a former army officer who rebelled last year saying he had been cheated out of the governorship of neighbouring Jonglei state in April elections.

The south has accused the north of backing Athor, an accusation he dismisses.

Southerners overwhelmingly voted to declare independence from the north in a January referendum promised in a 2005 peace deal that ended decades of north/south civil war.