The proposed law is modeled on the US system instituted after 9/11, which Washington announced yesterday would be abandoned by the end of April and replaced with a new plan to notify specific people about specific threats. Critics had complained the general colour alerts were unhelpful.

Russia has not specified how its three-level codes would work. But the push to pass the legislation underlines Russia's growing anxiety about its international security image as it tries to cope with terrorist attacks blamed on Islamist insurgents from the restive Caucasus region.

The measure was on the State Duma's agenda for February, but the vote was rushed forward after the bombing at Domodedovo Airport, Russia's busiest. No claim of responsibility for the bombing has been made and officials have not publicly identified any suspects. But, media reports say investigators are focusing on insurgents from the Caucasus region. Chechen rebels have claimed responsibility for a number of deadly attacks over the years, including ones against the Moscow subway and suicide bombings of two planes that took off from Domodedovo in 2004.

The Monday afternoon blast tore through the meeting area for international arrivals at Domodedovo. Some 180 people were injured, 129 of whom remained hospitalised today, according to the Health Ministry.

Authorities have not released an account of how the bombing took place, and media accounts have cited various sources as saying it was a male suicide bomber or a female or that the bomb was remotely detonated.

The Interfax news agency today cited an unidentified law-enforcement source as saying that surveillance video showed an unaccompanied male suspected suicide bomber, clad in a black jacket and baseball cap, standing in the area for about 15 minutes before the blast.

Some news reports have shown photos of a severed head believed to be that of the bomber and say the head has been sent to a forensic laboratory for DNA analysis. After the blast, suspicion initially fell on Chechen insurgents who have fought Russian forces since 1994 and who have claimed responsibility for an array of previous attacks, including last year's double suicide bombing of the Moscow subway that killed 40 people. However, Prime Minister Vladimir Putin said preliminary evidence showed no connection with Chechnya.