Hizbullah and Amal on Thursday openly accused the Lebanese Forces of launching an “armed attack” on their supporters in the Tayyouneh area, which had during the day witnessed hours-long armed clashes reminiscent of the beginning of the 1975-1990 civil war.

The United States on Thursday urged an easing of tensions in Lebanon after deadly violence in a Beirut suburb sparked fears of a return to sectarian strife.

U.N. Special Coordinator for Lebanon Joanna Wronecka expressed "deep concern" Thursday over the outbreaks of violence that took place in and around Tayyouneh and resulted in several deaths and injuries.

Condemning the "use of armed violence outside of state authority," she underscored the need for restraint and for maintaining calm and stability and ensuring the protection of civilians.

Tarek Bitar, the young and discreet judge investigating last year's devastating Beirut port explosion, is arguably the most exposed man in the country.

France on Thursday expressed concern over the deadly unrest that erupted in Lebanon over the investigation into last year's Beirut port blast and urged all parties to calm the situation.

With gun battles breaking out in Tayyouneh Thursday during a protest against Judge Tarek Bitar, AFP looks at how the apocalyptic blast that devastated the port of Beirut last year has rocked the country.

Amal Movement and Hizbullah accused "armed and organized groups" of assaulting their supporters in Tayyouneh, in a joint statement Thursday.

President Michel Aoun has made calls to follow up on the developments of the Tayyouneh clashes “in order to address the situation and take the necessary action to restore calm to the region,” the Presidency said Thursday.

Aoun called Prime Minister Najib Miqati, ministers of defense and interior Maurice Slim and Bassam Mawlawi, and Army Commander General Joseph Aoun.

Former Prime Minister Hassan Diab returned to Beirut on Wednesday evening, amid a political campaign led by Hizbullah and Amal against Lead investigator in Beirut port blast, judge Tarek Bitar.

Bitar in August subpoenaed Diab for interrogation on September 20 after he failed to show up for questioning.

Heavy fighting claimed at least six lives and left dozens wounded in and around the Tayyouneh area on Thursday as an escalation of tensions around last year's massive portside explosion turned parts of Beirut's southern edge into a war-zone.

The army deployed tanks and troops to quell street battles that sparked memories of the 1975-1990 civil war for a city already traumatized by last year's blast disaster and Lebanon's worst-ever economic crisis.