''The battle against terrorists must be pursued unceremoniously,'' Mr Medvedev was quoted as saying at a meeting with members of his national security council in the southern Russian city of Stavropol.

''They must be liquidated without emotion or hesitation, or else we will not succeed,'' he said, according to Russian news agencies.

Mr Medvedev spoke two days after a truck packed with explosives rammed the gates of a police station in Ingushetia, a province neighbouring Chechnya, and exploded in a suicide attack that killed 24, wounded 130 and left nine missing.

The Russian president said the situation in the north Caucasus, an area located in the south of the country, was still insecure.

In April, Russia ended a 10-year anti-terrorism operation in Chechnya. ''Not long ago, the notion took hold that the situation in the Caucasus, in connection with manifestations of terrorism, had distinctly improved,'' he said.

''Unfortunately, recent events demonstrate that this is not the case.''

Mr Medvedev said the fight against terrorism in the volatile region would be expanded and would incorporate ''different approaches'', but did not elaborate on what measures would be taken.

''If this work is halted, very serious events will begin to occur [in the region],'' he said.

He cited foreign elements as a factor fomenting instability in the region, but said the root cause of the problem was within Russia itself, referring specifically to corruption among law-enforcement personnel.

Deadly attacks by Islamist militants on Russian law enforcement personnel in the north Caucasus have become a daily occurrence, but Monday's bomb attack in Nazran, the main city in the province of Ingushetia, was unusually large.

NATO chief Anders Fogh Rasmussen wrote to Mr Medvedev condemning the attack.

The NATO secretary-general offered his condolences to the Russian people, saying ''this tragic loss of life and suffering underscores yet again the grave danger that the terrorist threat poses to all of us,'' a spokeswoman for the alliance said.

Further unrest flared in the Caucasus on Wednesday, with an officer from Russian security service FSB shot dead in Ingushetia, six rebels killed in Dagestan and four more militants killed in Chechnya, agencies reported. AFP