The U.N. secretary-general is calling on all parties in Lebanon to show restraint, as a second day of sectarian clashes threatens to escalate that country's political crisis. From United Nations headquarters in New York, VOA's Margaret Besheer has more.

Ban Ki-moon's Middle East envoy, Terje Roed-Larsen, said the U.N. chief is very concerned about clashes this week between Shiite supporters of Hezbollah and Sunni supporters of the pro-Western government.

"The secretary-general is deeply concerned about the evolving situation in Lebanon. ? He calls for all parties now to show restraint, to find a solution to the current impasse and the current violence through peaceful dialogue," he said.

Fierce street fighting continued Thursday in Beirut, as well as in the Bekaa Valley, shutting down the airport, seaport and roads.

In televised remarks Thursday, Hezbollah chief Hassan Nasrallah upped the rhetoric saying the Lebanese government's allegation that his group's private telecommunications network is illegal amounts to a "declaration of war."

In New York, U.N. envoy Roed-Larsen warned that Lebanon could slide deeper into conflict.

"I think Lebanon, for a long time now - for several months or more - has been on a slippery slope of violence and turmoil. At the core of this are political issues. One of the pressing issues at hand is to have parliament meet and to allow it - according to constitutional rules - to elect a new president," he said.

Lebanon's parliament has not met in two years and the country's political crisis has deepened over the past six months, as the legislature keeps postponing a vote on a new president because of factional in-fighting.

The Security Council met Thursday to hear the secretary-general's semi-annual report on the implementation of resolution 1559, which calls for the disarming and disbanding of all militias in Lebanon.

Roed-Larsen, who delivered the report, said there has not been any tangible progress on that front over the past six months and that the situation has instead regressed.

"Unfortunately, the clashes which we have seen over the last few days and also the arming of the main militias in Lebanon, has unfortunately, led over time to the establishment and rearming of a range of other militias in Lebanon," he said.

He warned that Lebanon faces serious challenges not seen since the end of its 15-year civil war. He said political paralysis and the arming of militias are threats to Lebanon's ability to operate as a sovereign, democratic and independent state.

In a statement, the Security Council expressed its deep concern about the unrest and urged calm, saying the best way to diffuse tensions and avoid further instability is to resolve the political crisis, calling on all sides to work together.