Return of the bus bomb has struck terror into the heart of Tel Aviv

In one week, two things have changed in Israel's beating heart and biggest city, Tel Aviv.

A few hours ago, a dull thud heard in the city centre heralded the return of a Tel Aviv terror: the bus bomb.

For the first time in six years, Palestinian militants have detonated explosives on a crowded bus in the middle of the day, injuring more than 20 people.

No-one was killed, but the attack has struck terror across the city.

No group has the attack yet, though imams at mosques in Gaza have boasted that the fighters of Hamas, from its Al Qassam brigades, planted the bomb on the bus.

If Hamas is responsible, it is a remarkably provocative act.

But let's say it immediately: It is no less provocative than the Israeli air strikes on Hamas buildings in Gaza which have only intensified, even as both sides proclaim their willingness to end this spasm of violence.

Whoever did this sent a message. The bomb, detonated not by a suicide bomber but by remote control, exploded as the bus was approaching Israel's Defence Ministry - the timing wholly deliberate.

Along with the blast on the ground in Tel Aviv, the city has been shaken this week by the threat from the air.

A truce may be near, but the people of Tel Aviv are still scanning the skies for signs of Palestinian rockets, still alert for the sirens that will give them twenty seconds to find cover.

This too is new, or at least something Tel Aviv hasn't experienced for 20 years.

The men and women who plan Israel's military strikes in Gaza may calculate that the bomb on the bus crosses another of their "red lines" - that it is a step too far for which Hamas must be punished even further.

Israel's logic has always been that Palestinians must pay a heavy price for every attack in order to deter it from trying the same thing again. A truce in Gaza may now be a little further off.

A century ago, an armistice was announced across the Western Front of Europe. But before the quiet, in the final few hours of war, more than ten thousand men fell in a final barrage of fury and frustration, bombs and bullets.

In Gaza today, and in Israel, millions of ordinary people are paying homage to their Gods for peace.

But they are deeply fearful of the final hours of revenge, retribution and retaliation that so often comes before the silence.