Beirut  - Lebanon observed a national day of mourning Wednesday to protest Israeli attacks on the Gaza Strip, as a high- state of alert at the Lebanese-Israeli border was registered.

Most government institutions were closed, but private businesses remained opened.

Flags flew at half mast on most government buildings in Beirut in a show of solidarity with the Gaza victims.

The Lebanese cabinet on Tuesday approved one million dollars of immediate relief aid to victims of the Israeli attack on Gaza and called for speeding up efforts to hold an extraordinary Arab summit conference.

In a related development, Lebanese security sources in southern Lebanon said Wednesday that Israeli soldiers on the Lebanese-Israeli border were put on a state of high alert in anticipation of possible rocket attacks by Palestinian factions or the Islamist Hezbollah group from Lebanon.

Heavy Israeli patrols were seen roaming roads adjacent to the Lebanon border.

Israeli media quoted Prime Minister Ehud Olmert's spokesman Mark Regev as saying the Jewish state was worried about the threat posed by Hezbollah on Israel's northern frontier.

UN peacekeepers and Lebanese troops have also stepped up patrols along the border with Israel after eight rockets were dismantled last week in south Lebanon following the Israel's massive military operation in Gaza.

UN deputy assistant spokeswoman in southern Lebanon, Andrea Tinti, said the United Nations Interim Forces in southern Lebanon (UNIFIL) were closely observing the situation.

The UN mission in southern Lebanon was enhanced in 2006 to 13,000 troops to monitor a fragile ceasefire which ended 33-days of fierce fighting between the Lebanese Shiite movement Hezbollah and Israel. (dpa)