RAS AJDIR, Tunisia (AP) — Tunisia closed its main border crossing with Libya on Friday after thousands of stranded Egyptian and foreign nationals, fleeing militias' fighting and violence in Libya, tried to break through the passage, the Tunisian news agency said.

It was the second eruption of unrest at the border in as many days, as thousands of Libyans stream into neighboring Tunisia, along with foreign nationals. Tunisia is the only escape route as fighting escalates in the Libyan capital, Tripoli, where rival militias have been battling for weeks for control over the airport.

Friday's unrest took place when thousands of Egyptians, barred from entering Tunisia because they had no visa, held a protest then broke through part of a fence at the Ras Ajdir crossing, Tunisian security officials said. The police responded by shooting in the air and firing tear gas. The officials spoke on condition of anonymity because they were not authorized to speak to the press.

An Associated Press reporter at the crossing said no one managed to make it to the other side and security forces used vehicles to physically block access. After a Tunisian police officer was wounded by gunfire from the Libyan side of the border, authorities closed the crossing, the official Tunisian news agency TAP said.

A day earlier, two Egyptians were killed during a similar protest demanding to be let through. Tunisian officials say thousands of Libyans have been crossing the border each day the past week.

Libya is witnessing its worst factional violence since the downfall of the longtime dictator Moammar Gadhafi in 2011 civil war. Along with the fighting in Tripoli, which the Health Ministry said has killed 214 people and wounding more than 980 others, Islamic militias the past week overran army bases in Libya's second largest city, Benghazi, and claimed control of the city.

On Friday, a powerful explosion ripped through the main police headquarters in Benghazi, nearly flattening it, witnesses said. The blast shook nearby houses and echoed across the eastern city.

The headquarters had been empty because of earlier shelling by militiamen. Friday's blast appeared to be from explosives planted inside the building, said witnesses at the site. They spoke on condition of anonymity, fearing for their own safety. Police officials in Benghazi, could not be reached for comment.

The spiral of violence in the country's two main cities prompted calls for public protests Friday against militias.

"It's time for a popular uprising to rescue Libya," said Abdel-Moneim al-Yassir, a lawmaker in the outgoing parliament and head of its National Security Committee. He called for protests on his Facebook page, saying they were "the only solution ... to put an end to the situation by disarming and demobilizing militias under a national accord."

The Tripoli violence erupted in early July when militias originally from the western city of Misrata, which are allied to Islamist politicians, carried out a surprise attack on militias from the western town of Zintan who control the airport. The move was in retaliation for a months-long campaign aiming to crush Islamic militias being waged by army troops led by a renegade general, Khalifa Hifter.

The battles have destroyed parts of Tripoli's international airport, and shelling earlier this week hit three oil depots, sparking a raging fire that firefighters have struggled to put out amid the continued fighting. The National Safety Agency, which oversees emergency services, said that one depot was still on fire on Friday.

The fighting in Tripoli and Benghazi is seen as a push by Islamists and their allied militias to shift a longtime balance of power among Libya's many militias.The militias emerged after the 2011 civil war that led to the ouster and death Gadhafi. Since then, the central government, police and military have largely had no authority.

The intensity of the fighting prompted foreign diplomats to flee the country along with thousands of Libyans and foreign workers.

But with Tripoli International Airport closed by fighting, there are few options besides the Tunisian crossing.

___

Almosmari reported from Benghazi, Libya. AP correspondent Bouazza Ben Bouazza in Tunis, Tunisia, contributed to this report.