TRIPOLI, Sept. 1 (Xinhua) -- France, Italy, Britain and the United States on Saturday issued a joint statement condemning the escalation of violence between government forces and armed groups in the Libyan capital Tripoli since Monday.

The continued escalation of violence in and around Tripoli caused many casualties and continues to endanger the lives of innocent civilians, the statement said.

The statement urged the warring parties to stop all military actions, warning "those who tamper with security in Tripoli or elsewhere in Libya that they will be held accountable for any such actions."

The statement also stressed support for the action plan on Libya proposed by UN envoy to Libya Ghassan Salame, and called on all parties to "refrain from any action that would jeopardize the political framework established by the UN-led mediation to which the international community is fully committed."

The interior ministry announced on Friday a cease-fire in Tripoli under the auspices of the United Nations. However, witnesses confirmed that heavy gun firing and explosions could still be heard in parts of the city.

Southern Tripoli has witnessed violent clashes since Monday between government forces and armed militias, which have so far killed 41 people and injured 123 others.

The reasons for the clashes remain unknown, with growing tensions and military mobilization over the past few days between armed groups from outside and inside the city.

The Interior Minister Abdulsalam Ashour told a local TV channel on Monday that a cease-fire agreement in Tripoli had been reached. However, clashes occurred on Wednesday despite the announcement, according to a local security source.