Israel has been placed in a state of high alert on the eve of its 60th birthday over fears that terrorist attacks are being planned to spoil this week’s celebrations.

Amos Yadlin, Israel’s head of military intelligence, told the Knesset, the Israeli parliament, that terrorist organisations were preparing attacks.

In response, the number of officers sent by Shin Bet, the internal security service, to guard institutions in Israel and abroad has been doubled. Security on Israeli aircraft has been stepped up and the number of air marshals increased. Some civilian aircraft have been issued with antimissile protection.

Although Israel declared independence on May 14, 1948, independence day is celebrated in accordance with the Hebrew lunar calendar and will take place from sunset on May 7 to the following evening.

The security risk is heightened by the prospect of thousands of Israelis who live abroad coming home to celebrate the holiday with their families. Hundreds of prominent Jews are also on their way to demonstrate the strong bond between the Jewish diaspora and the state of Israel.

Potential attackers include Hamas, the Palestinian militant group – which has grown stronger in Gaza thanks to Iranian finance and training – and Hezbollah, in Lebanon, which promised retaliation earlier this year for Israel’s assassination of Imad Mughniyeh, one of its commanders, in Damascus.

Prominent visitors expected in Israel include George Bush, the US president, due next week.

- Ehud Olmert, Israel’s prime minister, faces mounting pressure to resign this week after being questioned by police over allegations of corruption.

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