The official says Thursday's protests drew thousands to the streets in several towns in the province of Aden.

The official says troops detained dozens of protesters. He spoke on condition of anonymity because he wasn't authorized to talk to the media.

The demonstrations came ahead of a key meeting of the "Friends of Yemen" donors group in New York on Friday.

The protesters carried flags of former South Yemen and anti-North placards.

Tribal sources estimated that 8,000 people, most of them carrying firearms, took part in the demonstration in Loder, shouting slogans against Yemeni unity.

Last month, Loder was the scene of fierce clashes between Yemeni forces and alleged Al-Qaeda militants as Sanaa charged that members of the Southern Movement fought alongside Al-Qaeda.

A Southern Movement source said his supporters "carried arms after the Yemeni army, which has been imposing a blockade on Loder since August, threatened to crush the demonstration." "We took arms to defend ourselves," he said.

Protesters in Loder called in a statement "on south Yemenis to unite in the face of the barbaric military campaign by the occupation Yemeni forces against the people of Huta city in Shabwa province," where fierce fighting with suspected Al-Qaeda militants has been raging over the past six days.

The statement called on the international community and the "Friends of Yemen" group to "intervene to resolve the south Yemen issue."

"Resolving the southern cause is essential to resolving all problems facing Yemen ... Any solution that does not stipulate a final settlement for south Yemen will be without any value." Police dispersed a small group of demonstrators Thursday morning in Aden, the main city in south Yemen, eyewitnesses said.

Southern Movement spokesman Ahmad Al-Rabeezi said security forces arrested 12 people as they left a meeting in Aden province, where they were planning for the protests.

Police tightened security in Aden where supporters of the Southern Movement prepared to stage a demonstration in the evening, Rabeezi said.

The "Friends of Yemen" group aims to fight extremism and raise funds to tackle poverty in the Arabian Peninsula country.

"The (New York) meeting will review progress since the high-level meeting in London in January (and) give strong direction to future work of the Friends of Yemen," said a statement from co-chairs Yemen, Saudi Arabia and Britain.

The ministerial-level meeting will bring together donor states, other "Friends of Yemen" and Yemeni government representatives, at a time when the situation in Yemen has worsened.