Yemeni armed forces tightened security measures on Friday evening in the country's southern port city of Aden after secessionists called for massive rallies to mark a civil war anniversary, a police officer said.

The Yemeni troops were deployed on the streets in Aden as southern activists called for marking the anniversary of 1994 separatist rebellion that was quelled by the government, the local police officer told Xinhua on condition of anonymity.

"The army soldiers try to secure Aden's main entrances from any infiltration of separatist gunmen," the police officer said.

The pro-secession Southern Movement called for demonstrations across the country's south to mark the anniversary of a separatist rebellion which led to civil war on July 7, 1994.

"Thousands of southern protesters are determined to participate in the demonstrations... no one will deprive us from our right," a separatist told Xinhua anonymously.

"Blocking the roads by government troops and preventing southern youths from organizing their marches often prompt to violent clashes," he said.

Tension is high in Aden since security forces started to search al-Qaida militants last month who were accused of killing the top army commander who led the fight against the terrorist group in the southern regions.

The port city of Aden is a main stronghold of youth activists demanding independence for the south.

North and South Yemen unified peacefully in 1990, but the relationship deteriorated in 1994. Calls for separation in the country's southern regions were renewed in 2007.