The government of Muammar Gaddafi said NATO strikes on Tripoli have killed 31 people, adding that Western leaders were not seeking a peaceful solution but escalation.

Waves of NATO aircraft hit the Libyan capital in the most sustained bombardment of the city since Western forces began air strikes in March.

NATO warplanes struck the Libyan capital several times an hour, hour after hour.

Government spokesman Moussa Ibrahim told reporters it had been 'one of the most horrific days of attack', and the strikes had killed at least 31 people, including civilians.

Earlier Libyan leader Muammar Gaddafi promised that he would fight to the end, in a defiant speech broadcast on state television.

'We only have one choice: we will stay in our land dead or alive.'

He called on his supporters to gather at his Bab al-Aziziya compound.

NATO aircraft hit targets overnight in the Libyan capital in the vicinity of the vast compound, in the most sustained bombardment of the Libyan capital since Western forces began air strikes in March.

However, describing planes flying overhead and explosions around him, Col Gaddafi was defiant.

'We are stronger than your missiles, stronger than your planes and the voice of the Libyan people is louder than explosions.'

He said he was ready to unleash between 250,000 to 500,000 armed Libyans to swarm across the country to cleanse it from 'armed gangs', a reference to the rebels controlling the east of the country.

Aircraft struck different parts of Tripoli several times this afternoon, rattling windows and sending clouds of grey smoke into the sky.

Meanwhile, US President Barack Obama has said that it is just a matter of time before the Libyan leader is ousted.

At a joint news conference with German Chancellor Angela Merkel, Mr Obama described 'significant' progress in the NATO drive to protect Libyan civilians and rebels from attacks by Gaddafi supporters.

He said: 'What you are seeing across the country is an inexorable trend of the regime forces being pushed back, being incapacitated. I think it is just a matter of time before Gaddafi goes.'