AS Yassir Arafat’s condition worsened yesterday morning, Israeli warplanes were scrambled over south Lebanon in anticipation of a violent reaction from Palestinian refugees.

Although Israeli military aircraft routinely breach Lebanese airspace, the concentration of overflights reflected fears that Mr Arafat’s death would spark violence along Israel’s troubled northern border with Lebanon.

The Lebanese authorities also braced themselves for possible cross-border rocket attacks from Palestinian militants living in refugee camps in south Lebanon controlled by Mr Arafat’s Fatah faction.

Their concerns were stoked last week when suspected Palestinian militants fired a Katyusha rocket into northern Israel. Security officials suspect that the attack was a reaction to the announcement last week that Mr Arafat was seriously ill. The rocket exploded in a banana plantation in Western Galilee, causing no casualties. The strike, the first into Israel since a ten-day escalation along the border in April 2002, was hushed up by the Lebanese and Israeli authorities. Israel lodged a complaint with the UN peacekeepers in south Lebanon, but has accepted that a Palestinian group was the probable culprit.

A senior security source said that the Lebanese and Israeli authorities were worried that when Mr Arafat dies, Palestinians may seek revenge against Israel along the border. The Israelis may receive some help in maintaining calm from an unlikely source: Lebanon’s Hezbollah organisation.

Hezbollah militants are deployed along the 70-mile frontier and occasionally attack Israeli military positions in the Shebaa Farms, a strip of mountainside running along Lebanon’s southeast border with the Golan Heights. But Hezbollah is careful to protect its tactical control of the border, aware that the finely tuned rules that govern its clashes with Israel can easily be upset by unauthorised attacks.

Hezbollah’s fighters have been known to stop armed Palestinians on their way to the frontier and hand them over to the Lebanese authorities.

“Hezbollah and Israel treat each other with silk gloves,” the security source said. “It is a conflict that can be managed if there is a political will. The Palestinians, however, are volatile and pose a threat to everyone.”

As head of the Palestine Liberation Organisation, Mr Arafat ran a state-within-a-state in south Lebanon in the 1970s when Palestinian fighters regularly bombed northern Israel and staged cross-border raids.

Israel invaded Lebanon in 1982, driving the PLO out of the country, but abandoned its south Lebanon occupation zone four years ago.

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