Thai anti-government protestors have appealed to the European Union calling for observers to come to the rally site in central Bangkok in the hope of preventing "an imminent military crackdown".

In the letter presented by senior leaders of the anti-government protestors or Red Shirts to the European Union's ambassador it appealed for observers to "monitor the government's actions" amid fears of an "imminent military crackdown."

Leaders of the United Democratic Front against Dictatorship (UDD) said protestors faced the threat of tanks and impending bloodshed, and appealed to the European Union for help in averting "a human rights catastrophe".

The UDD protest site of the past month is in central Bangkok's retail and commercial area of Rajaprasong and bounded by five-star hotels and apartment buildings. At the site on Thursday several children and women were visible within the protest camp which is set on a main road.

Several thousand so-called Red Shirt protestors are barricaded in a three square kilometer area with home-made bamboo spears, stones and sling-shots. Many say they have no fear of the military. The army says up to 1,000 people in the area may have guns and weapons.

Most of the commercial businesses in the area have been shuttered with many facing massive losses in revenue from the weeks of protests.

UDD spokesperson Sean Boonpracong appealed to Thai military draftees sent to the site and preparing to complete two years of conscription not to fire upon the protestors.

"The people that they shoot could end up being your relatives and your friends," Boonpracong said. "You could go home as an honourable citizen or you could go home and be branded a killer all your life. You have yourself to decide ? do the right thing ? think about it."

The UDD protests largely support former Prime Minister Thaksin Shinawatra, with the backing of the opposition Puea Thai Party. Most supporters are largely the rural and urban working class and poor. Some analysts say the protests have led to a growing political influence of the Red Shirts ready to challenge the existing government and military.

Prime Minister Abhisit Vejjajiva, in recent interviews, says the government is looking to enforce the law while in parallel finding a political solution.

Government officials say they are trying to arrest people they call "terrorists," who they say have mingled with demonstrators and who are accused of firing on troops on April 10 during a clash with military. Since the Red Shirts began demonstrating in Bangkok last month, 27 people have died and almost 1,000 have been injured in clashes.

The government is also coming under pressure from several groups to end the protests and occupation. One group is the anti-Thaksin group the People's Alliance for Democracy or PAD. On Thursday the PAD rallied outside a military base where Mr. Abhisit and military leaders have remained since the protests began in mid-March.

At the rally, the PAD leaders called on the government to act "decisively" against those who breach the law.

Thailand is being gripped by the most severe political crisis in almost 20 years. In 1992 pro-democracy protestors clashed with the army when they opposed the military's appointment of a prime minister, Suchinda Krayprayoon. Over three days some 50 people died and hundreds were injured.