The buzz of lunchtime conversation this week around the cafes lining Bogotá's upmarket 93rd Street Park betrayed no hint of the state of emergency declared in Colombia in response to one of the most dramatic rebel attacks in recent times.

Normal life in the capital has continued, in spite of the deadly mortar barrage directed at President Alvaro Uribe's swearing-in ceremony on August 7. Few people have yet felt any effects of Mr Uribe's declaration of "domestic commotion", which over the next three months will allow the government to curtail some individual freedoms and impose tougher laws and security measures as it seeks to counter the Revolutionary Armed Forces of Colombia (Farc) and other criminals.

However, by preparing a legal crackdown, and by announcing a one-off tax on the wealthy that should raise $800m to pay for extra police and soldiers, Mr Uribe has sent a signal that re-establishing security tops his agenda. The message is directed particularly at the US.

In the months before Mr Uribe took office Washington had warned that Colombia needed to show more financial and moral commitment to solving its own problems if US aid, worth $1.7bn since 2000, was to continue to flow.

"This is a big positive and it will be for the Congress," said a senior US official who met Mr Uribe in Bogotá this week. "$800m is not a small amount of money." By October the US Congress will set levels of aid for Colombia for 2003.

Most Colombians appear broadly supportive of the government's assumption of emergency powers, which are allowed under the constitution. That feeling reflects unprecedented anger at the Farc's excesses, which was what helped elect Mr Uribe. He voiced his desire to hit back at the rebels in February, after peace talks were called off.

Ernesto Borda, of the political science department at Bogotá's Javeriana university, says the government is emphasising a show of national unity against the guerrillas. "The reaction of support has been unprecedented," he says.

This is the fifth time since 1991 that a government has declared a state of emergency. Yet doubts remain about how useful any wider government powers are likely to be. During the state of emergency the government will probably restrict freedom of movement and make it easier to arrest and question criminal suspects. The constitution allows "domestic commotion" to be declared for a 90-day period, renewable twice, so any tougher measures imposed should theoretically last only until May.

However, with the Farc having been active for 38 years, Gustavo Gallón, director of the Colombian Commission of Jurists, says the government's use of emergency powers is inappropriate. "There is a manipulation of the idea of a state of exceptional circumstances," he says. "The current constitution provides many tools for the government to use. But it has not done so."

The government disagrees. In fact it appears to be looking beyond a temporary emergency: it seems set to try to impose a stricter legal framework for as long as is necessary - "until the mortars stop falling", interior minister Fernando London~o told a local newspaper before the declaration of the emergency.

The government will probably try to reform Colombia's 1991 constitution, itself the result of peace agreements with other rebel groups, by inserting what it sees as more useful counter-terrorism laws.

Mr Gallón fears that Colombia is once again placing its faith in draconian solutions, which have been tried before with little success. "The government is manipulating the Colombian people. It wants them to believe that it needs more and more powers," he says. "But they don't need these powers to attack the Farc. This is a response of desperation."

Anti-terrorist legislation in countries such as Britain, France, Germany and Spain is tougher than anything under Colombia's "domestic commotion" rules, notes Tom Duggin, the UK's ambassador to Bogotá. He says there are controls available under the state of emergency that are justified by what he says are the conflict's new circumstances: "There has been a step change in the Farc's technology, and evidence of a well-trained urban militia in Bogotá."