As tension increases tonight in the Persian Gulf, US and British warplanes have been attacking artillery systems in the Iraqi no-fly zones.

The Pentagon said US warplanes conducted multiple strikes in Southern Iraq, striking anti-aircraft artillery, air defences and surface-to-surface missile systems.

There is a general perception that an all-out coalition assault on targets in Iraq is now only hours away.

Iraq has decidedly rejected a US ultimatum for its president and his sons to leave the country by 1am to avert war.

The United States and Britain have massed a total of some 280,000 troops around Iraq.

It was unclear whether the attacks were the precursor to the main coalition onslaught - expected to open with a massive aerial bombardment.

All are now only waiting for the final execute order - the signal toadvance and launch the invasion.

Throughout the day final preparations were being made by troops across the whole of the Gulf region, which saw a severe sandstorm of blinding grit anddust.

Pentagon officials have indicated that hostilities will begin with an intense air campaign, followed very quickly by soldiers on the ground.

The demilitarised zone extends 5km into Kuwait and 10km into Iraq. It was not clear how far in the troops had entered. UN observers pulled out of the DMZ on Monday.

Small groups of engineers slipped in last week to cut gates in the fence that marks the border between the two countries.

A trench, a sand wall and an electric fence extend along Kuwait's 200km-long land border with Iraq. The two countries also share a 40km-long sea border.

Tareq Aziz rumour

Earlier, Iraq confirmed that Deputy Prime Minister, Tareq Aziz, had not defected and continued to carry out his duties in Baghdad.

Mr Aziz gave a televised news conference this evening following the speculation he had fled to Kurdistan.

The British Foreign Office earlier said it was investigating a rumour that he had defected.

Security Council meeting

UN Secretary General Kofi Annan has meanwhile reminded the United States and Britain of their legal duty to protect Iraqi civilians in what he called the imminent disaster of war.

At the United Nations Hans Blix has expressed frustration at the failure of three and a half months of arms inspections.

Russia and France have again expressed their opposition to the military campaign but say plans must now be made for the looming humanitarian crisis.

The UN Security Council met to consider the UN's role in handling the probable humanitarian crisis following an invasion of Iraq.

The German Foreign Minister, Joschka Fischer, said it was still possible to peacefully disarm Iraq and that Berlin therefore 'empatically rejected' war on Baghdad.

Mr Fischer said the Council was in danger of becoming irrelevant if it did not act, even at this late stage.

Russian Foreign Minister Igor Ivanov stressed that Washington had no legal authority for an attack.

He said it would have 'serious negative consequences', including the break-up of the international coalition against terror.

Five countries, most of them leading critics of military action against Iraq, are attending at Ministerial level. The rest are represented by their Ambassadors.

Turkish parliament to vote on use of airspace

The Turkish government has approved permission for US and UK planes to use its airspace but will not allow them access to military airbases, even for refuelling.

Earlier, the US withdrew a $6 billion aid package for Turkey after its parliament failed to approve the deployment of 62,000 US troops in the country.

The Prime Minister, Tayyip Erdogan, said Turkey's talks with the US were now only on military and political issues, not economic, and added the parliament resolution would not give Washington the right to use Turkish airbases.

Saudi Arabia proposes exile for Saddam

Saudi Arabia has proposed for the first time that Iraqi President Saddam Hussein should go into exile as a last-ditch effort to avert war.

'The kingdom, and other parties, are exerting maximum effort to prevent a devastating war and have proposed the idea of exile for Saddam and securing a safe haven for him and his family,' a diplomatic source said.

Earlier, Bahrain's King Hamad offered asylum to Saddam Hussein in a final attempt to avert war.

Iraqi leaders step up criticisms of US

The speaker of the Iraqi parliament said today it would be 'unthinkable' for President Saddam Hussein to comply with the US ultimatum to flee the country.

Saadoun Hammadi made the statement after an emergency session of the Iraqi parliament which concluded with lawmakers sending a letter of allegiance to Saddam Hussein and vowing to lay down their lives defending Iraq.

Iraq's ambassador to the UN has said his country wants to avoid war at all costs. Mohammed Aldouri urged the UN Secretary-General, Kofi Annan, to make a last-ditch effort to prevent an invasion of his country by US-led forces.

Overnight, people continued to flee the capital as the deadline for war approaches. International aid agencies are warning that they will face enormous difficulties with the humanitarian crisis they are expecting, if there is a war in Iraq.

With as many as two million people likely to flee their homes, Oxfam and Amnesty International are appealing to all neighbouring countries to open their borders and accept refugees.

Foreign nationals are leaving neigbouring Kuwait on the advice of their governments. Boarding the last BA flight out of the country before probable war on Iraq, many said they resented the disruption to their lives.

Also in Kuwait, a severe dust storm which hit the country today was expected to subside by this evening.

The recurrent dust storms have been hard on the more than 170,000 US and British soldiers deployed along Kuwait's northern desert border, waiting for the green light from Washington to invade Iraq.

Many have complained of having to repeatedly clear the dust from their gun barrels and sweep out their sleeping quarters.