Tripoli, Libya (CNN) -- Hundreds of people gathered Saturday in Tripoli's Martyrs Square to mourn the victims of fighting in the capital a day earlier.
At least 43 people were killed and 460 others wounded on Friday in the bloodiest day of fighting here since the fall of Tripoli in 2011, the state run Libya News Agency LANA reported.
The fighting broke out after protesters arrived at the Tripoli headquarters of militias from the coastal city of Misrata.
Protesters and witnesses said militiamen opened fire on the protesters who marched on Gharghour, a southern district of the capital where Misrata militia are based, in an effort to evict the armed groups.
TV footage aired on the privately owned al-Nabaa channel showed militiamen, in a truck equipped with what appeared to be an antiaircraft mounted on the back, opening fire directly at protesters.
The armed confrontation lasted for hours as protesters returned with weapons and militiamen from different parts of the capital.
The sound of heavy gunfire, artillery and explosions echoed across Tripoli on Friday night and clashes erupted Saturday east of the city.
Libyan officials said fresh fighting broke out in the district of Tajoura, an eastern entrance to the capital, where heavily armed militiamen from Misrata were trying to enter Tripoli.
At least one person was killed and eight other were wounded in the early morning fighting, LANA reported. More fighting was reported in the area in the afternoon.
Prime Minister Ali Zaidan warned Saturday in a news conference that the arrival of any forces from outside Tripoli would lead to a serious escalation.
"The coming hours and days will be decisive for the future of Libya," Justice Minister Salah Marghani told reporters.
Tensions were running high Saturday on the streets of Tripoli as militiamen fortified parts of the city, setting up roadblocks and closing off some roads leading into the capital.
The scene at Martyrs Square was an emotional one as people gathered for the funerals. Hours earlier, the government announced a three-day, nationwide period of mourning.
Some families marched through the square carrying pictures of the dead and coffins covered by the Libyan flag.
A local official read a statement to the crowd blaming the prime minister and the government for the situation.
"We will continue on this path to liberate Tripoli from these militias," the official said.
Meanwhile, much of the international community, including the United Nations and the European Union, condemned the violence and called for restraint and calm.
"The United Nations Support Mission in Libya (UNSMIL) strongly condemns the violence which took place in Tripoli on Friday 15 November, resulting in the tragic loss of life among civilians, and calls for its immediate cessation as well as supporting the efforts by authorities to restore calm, stop the bloodshed and ensure security and stability for all Libyans" UNSMIL said in a statement on Saturday.
U.S. Secretary of State John Kerry called for restraint. "Libyans did not risk their lives in their 2011 revolution for this violence to continue," he said in a statement. "If a free people are going to succeed in forging a peaceful, secure, and prosperous country with a government based on the rule of law and respect for human rights, then there can be no place for this kind of violence in the new Libya."
Anger against the various militias has been mounting for months in Tripoli and other parts of the country, including in the eastern city of Benghazi, which has been gripped by increasing violence, including political assassinations.
Friday's protest, which was organized in part by the Tripoli Local Council, occurred after heavy fighting in the heart of the capital last week between the Misrata militiamen and other groups from Tripoli.
Militiamen from Misrata and a number of other Libyan cities entered Tripoli during the fight for the capital in August 2011 and have stayed, establishing bases in different parts of the capital.
On Saturday, Zaidan renewed the government's calls for armed groups to leave the capital, reiterating a decision passed by lawmakers months ago, one that has yet to be implemented.
"The government has decided to contact all armed groups in Tripoli and inform them about the (General) National Congress's decision for them to leave Tripoli and it should be implemented as soon as possible" Zaidan told reporters.
But many observers were skeptical about the ability of the weak central government to enforce this decision. The government has not been able to rein in militia groups with various regional, tribal and political loyalties.
Last month, Zaidan was kidnapped by a militia in Tripoli group and released a few hours later by another militia group.
The government has also been struggling with its plans to build an army and police. Many militia members are on the state's payroll, but continue to operate freely with no government control or accountability.
"As long as militias and armed groups are not held to account for crimes they commit, innocent people will continue to die" Said Hanan Salah, a Libya researcher for Human Rights Watch "The government has a responsibility here to bring the perpetrators of these crimes to justice and hold them accountable for their acts."
CNN's Mohammed Tawfeeq, Nana Karikari-apau and Brian Walker in Atlanta contributed to this report.