Parts of the Gaza Strip have been reoccupied by Israeli troops: the move was ordered overnight after the mortar attack by the militant Islamic group Hamas on Sederot, a town well inside Israel.

That in turn was a response to what they called the assassination of one of their own activists.

The spiral is horribly familiar - but the Israeli move seems to elevate the latest conflict onto a new level.

The Gaza Strip, and parts of the West Bank, were handed over to the Palestinian Authority in the mid-90s.

Short stay?

It was the culmination of the Oslo peace process, and a move of huge significance.

Gaza: Territory ceded by Israel under the Oslo peace accord

But in recent months the Israelis have complained again and again that Yasser Arafat has done nothing to stem the violence in the areas under his control.

Today the patience of the new Prime Minister, Ariel Sharon, snapped. The reoccupation is supposed to be temporary, but the provocation is obvious.

The Israeli Government has made it clear that it does not intend to keep its troops in the Gaza Strip.

The government spokesman, Dr Raanan Ghissim, said a response was 'required' after mortars wire fired at innocent civilians.

Show of strength

Picking up the pieces: A Palestinian officer

So is this move by the Israelis a significant stepping up of Prime Minister Ariel Sharon's hard-line policy against the Palestinians?

Dr Rosemary Hollis, of the Royal institute for International Affairs, said Mr Sharon had always been against the Oslo peace accord.

For those who were closely involved in the process which led to the establishment of the Palestinian Authority - and the peace that was supposed to flow from it - the latest developments are desperately worrying.

One was Yossi Beilin, the former Israeli Justice Minister. He said the conflict was 'so far from our dreams'.

He went on to say it was 'dangerous' to occupy territory that had formally been handed over. A likely consequence was to be a further tightening of tension.