Security is tight in the Sri Lankan capital Colombo on Monday (July 31) as a top Tamil Tiger rebel said the country's four-year-old ceasefire is now void and the island's two-decade civil war is back on. S. Elilan, head of the Tigers' political wing in the restive eastern district of Trincomalee, said army troops had resumed a bid to advance towards land they control in the east and had fired artillery and mortars at their territory in the north. "The ceasefire agreement has become null and void at the moment," Elilan told Reuters by telephone from Trincomalee, adding government troops were continuing an advance towards their forward defence line in the east in a water supply dispute. "The war is on and we are ready," added Elilan as the guerrillas and the military entered a sixth straight day of fighting. Vehicle checkpoints were deployed in the capital Colombo as increased security measures set in. A political analyst said the situation was serious even though the announcement was not made by the top Tamil Tigers hierarchy. "It is a comment by an LTTE (Tamil Tigers) political leader, rather than an authoritative statement by the organisation. But nonetheless it is very serious," said Dr. Paikiasothy Saravanmuttu. "Apart from the obvious humanitarian considerations, there is the imminent possibility of a pitched battle between the two sides, which could well spread into a Eelam War 4 or whatever. And we are also in a situation in which we are talking about truce monitors leaving with no one exactly keen enough to replace them." The rebels, angry at President Mahinda Rajapakse's outright rejection of their demand for a separate homeland for ethnic Tamils in the north and east, have pulled out of peace talks indefinitely and have been cranking up the rhetoric for months. The Tigers say Sri Lanka's air force killed 15 rebels in five days of aerial bombing in the east and injured several others. The military said the death toll was much higher. In Colombo, residents were still clinging on to their hopes for peace. "No country wants a war. It is the ordinary people who will be destroyed by it. Therefore we do not want war. Any country will hope for peace," said rickshaw driver Akram Yousef. Many diplomats fear Black Tiger suicide bombers, blamed for a failed assassination attack on the army commander, could bring the war to Colombo, further hammering investor confidence in the $23-billion economy.