Some relatives said the use of such pictures was distasteful

Some of the families have complained that the images exploit those killed in the attacks and are in poor taste.

"It's totally disgusting," said Dawn Peterson, whose brother died in the attack on the World Trade Center.

A White House spokesman defended the election ads, saying they emphasised Mr Bush's leadership at a time of terror.

"September 11th was a defining moment for our nation," spokesman Scott McClellan said.

"It was an experience that all Americans shared. It is the reason we are still at war on terrorism."

BBC Washington correspondent Rob Watson says President Bush is campaigning on the basic pitch that you don't change leaders during a time of war.

But this controversy shows it is a pitch that will have to be handled with sensitivity if it is not to backfire, our correspondent says.

Contentious images

The four television advertisements, which began showing on Thursday across the US, marked the beginning of the Bush administration's campaign for the 2004 presidential elections.

I'm optimistic about America because I believe in the people of America George W Bush in campaign ad Watch a George Bush advert

Among the images shown in two of the advertisements are images of firefighters carrying a body, draped in a US flag, from the rubble at Ground Zero, where the World Trade Center once stood.

The International Association of Fire Fighters condemned the decision to use their images and said the US president was being hypocritical.

"We're not going to stand for him to put his arm around one of our members on top of a pile of rubble at Ground Zero during a tragedy and then stand by and watch him cut money for first responders [emergency services]," he said.

'Tasteful ad'

Other relatives said they felt their loved ones were being used to score political points.

"Families are enraged," victims' advocate Bill Doyle, who lost his 25-year-old son in the attacks, told Reuters news agency.

"What I think is distasteful is that the president is trying to use 9/11 as a springboard for his re-election."

"It's entirely wrong. He's had 3,500 deaths on his watch, including Iraq".

However some victims' families disagreed, saying they found nothing offensive in the use of such images.

"I don't have a problem with his pointing to his leadership at that time," one woman, who lost her sister, told Reuters.

"He helped us weather it. To me it was a tasteful ad."