BEIRUT, Nov 25 (Reuters) - Hezbollah leader Sayyed Hassan Nasrallah warned Israel on Sunday that thousands of rockets would rain down on Tel Aviv and cities across the Jewish state if it attacked Lebanon.

Speaking four days after the ceasefire which ended a week of conflict between Israel and the Islamist Hamas rulers of Gaza, Nasrallah said Hezbollah's response to any attack would dwarf the rocket fire launched from Palestinian territories.

"Israel, which was shaken by a handful of Fajr-5 rockets during eight days - how would it cope with thousands of rockets which would fall on Tel Aviv and other (cities) ... if it attacked Lebanon?" Nasrallah said.

The Fajr-5s, with a range of 75 km (45 miles) - able to strike Tel Aviv or Jerusalem - and 175 kg (386 lb) warheads, are the most powerful and long-range rockets to have been fired from Gaza.

But Hezbollah, which fought Israel to a standstill in a 34-day war six years ago, says it has been re-arming since then and has a far deadlier arsenal than Hamas. Nasrallah has said Hezbollah could kill tens of thousands of people and strike anywhere inside Israel if hostilities break out again.

"If the confrontation with the Gaza Strip ... had a range of 40 to 70 km, the battle with us will range over the whole of occupied Palestine - from the Lebanese border to the Jordanian border, to the Red Sea," Nasrallah said.

Hezbollah could hit targets "from Kiryat Shmona - and let the Israelis listen carefully - from Kiryat Shmona to Eilat", he said, referring to Israeli's northernmost town on the Lebanese border to the Red Sea port 290 miles further south.

The movement has warned that any Israeli attack against the nuclear facilities of its patron Iran, which has armed and funded the Lebanese Shi'ite Muslim militant group, would inflame the Middle East - though it has not specified its own response.

In a move it said showed it could penetrate deep inside Israeli defences, it flew a drone over Israel last month. The drone was shot down after flying 25 miles into southern Israel.

Israel says its Iron Dome missile defence system knocked out 90 percent of the rockets fired from Gaza which were on course to hit populated areas.

TENS OF THOUSANDS MARK ASHURA

Nasrallah, who has lived in hiding since 2006 to avoid assassination by Israel, was speaking by video-link to tens of thousands of Shi'ite faithful in southern Beirut commemorating Ashura, the day when the Prophet Mohammad's grandson Hussein was killed in battle 13 centuries ago.

Wearing a black turban and robes in a sign of mourning, the 52-year-old cleric said his Shi'ite movement wanted to prevent sectarian tension in Lebanon - fuelled by the civil war in Syria - plunging his country into renewed conflict.

"We want to avert strife and Israel is our only enemy. We have no enemies in Lebanon," Nasrallah said.

Many Sunni Muslim political leaders blamed Hezbollah's ally Syria for last month's bomb attack which killed a top intelligence official and plunged Lebanon into political crisis.

The opposition March 14 coalition blamed Syria for the assassination and called on the Lebanese government, dominated by allies of Hezbollah and Syria, to quit.

Sporadic clashes have erupted since then, including a shootout in the southern city of Sidon two weeks ago when three people were killed after supporters of a Sunni cleric tried to tear down Shi'ite Ashura banners.

On Saturday the army said it arrested five people and seized 450 grams (1lb) of explosives in Nabatiyeh on the eve of an Ashura march in the southern Lebanese town which was attended by thousands of Shi'ite mourners, many striking their heads with blades to draw blood to mark the tragedy of Hussein's death.

Security sources said the arrested men were Syrians suspected of planning an attack on the Ashura processions but Nasrallah, speaking late on Saturday, suggested they were trying to send arms to the conflict in Syria.

"We already know that many Syrians arrive in Lebanon to buy weapons," he said. "Neither weather nor rain can frighten us, nor can explosions or security threats stand between us and Imam Hussein".