Some 23 opposition leaders from Yemen's southern regions, who were among the opposition's newly- established 143-member National Council against President Ali Abdullah Saleh, announced their withdrawal from the council in a statement issued late Friday.

The 143-member National Council was formed on Wednesday, a day after Saleh, who is in the Saudi capital of Riyadh for rehabilitation after he was injured in a bomb attack on his palace in June, vowed in a speech to return soon to Sanaa to resume his duties until 2013.

"We were surprised that our names were included in the list of National Council without acknowledging us," said the joint statement by the 23 opposition southern leaders, including former president Ali Nasser Mohamed, former prime minister Haidar Abu Bakr al-Attas and head of Islamic Islah (reform) party in the southeastern province of Hadramout.

The 23 leaders also said they refused to join the council because it lacked of balance between members from the south and north.

"Any national council with responsibility of leading the people 's peaceful revolution to overthrow the remains of Saleh's regime should be composed of fifty-fifty membership between the southern and the northern provinces," they said in the statement, which was signed by the leaders and published by the opposition's key media outlet almasdar.us.to.

They also accused the leaders of the opposition coalition Joint Meeting Parties (JMP) of ignoring what they called "the Southern Peaceful Movement," which included southern activists who have been seeking to secede southern Yemen from the north since 2007.

"As well as your (JMP's) ignorance to the Southern Cause and its Southern Peaceful Movement, many of whose activists were killed by government forces during previous clashes in the southern provinces, was another main factor behind our refusal to join the National Council," they added.

The south and north Yemen unified peacefully in 1990, but the relationship deteriorated by 1994, when a southern insurgency was quelled in a civil war. Calls for separation were renewed in early 2007.