Dozens of protesters in Aden called Friday for the secession of southern Yemen, before police moved in to disperse them, witnesses said.
Security forces -- backed by tanks -- fanned out around the capital to head off the so-called "day of rage" supported by Yemen's secessionist Southern Movement.
Dozens of protesters nevertheless took to the streets in the districts of Crater, Khor Maksar, and Al-Mansura, chanting "out occupation," before they were dispersed, witnesses told AFP.
In Al-Masura, police fired warning shots and tear gas to disperse the crowd.
The Southern Movement, a coalition of groups seeking autonomy or secession of the once-independent South Yemen, has expressed its support earlier this week to Facebook calls for a "day of rage" in the south.
Further east, several hundred people, led by a local separatist leader, Tareq al-Fadhli, took to the streets of Zinjibar, capital of Abyan province, with banners calling for an end to "the occupation".
No clashes were reported despite a heavy security and military deployment.
Police meanwhile fired warning shots and tear gas to disperse a demonstration in Hadramawt's provincial capital Mukalla, in the southeast, where protesters blocked roads and set car tyres alight, witnesses said.
South Yemen, where residents complain of discrimination by the Sanaa government in the allocation of resources, is frequently the scene of unrest.
The south was independent from 1967 until 1990 when it united with the north. It launched an abortive secession bid in 1994 and is still home to an active secessionist movement.
Yemen, the Arab world's poorest country and the ancestral homeland of Osama bin Laden, has also been struggling to combat an Al-Qaeda resurgence as well as Shiite unrest in the north.