* Red Cross says shells kill aid worker
* Tiger suicide boats attack troops
* End of India polls could usher in final assault
* Satellite photos evidence of shelling-rights group
By C. Bryson Hull
COLOMBO, May 13 (Reuters) - Shelling killed a Red Cross worker inside Sri Lanka's war zone on Wednesday, the aid agency said, while troops and the Tamil Tigers battled in an intensifying fight to the finish of Asia's longest modern war.
Two senior military sources, speaking on condition of anonymity, said heavy confrontations were picking up around the 2.5 square km (1 sq mile) combat zone where the Tigers are surrounded, and that some civilians were trying to flee.
The seeming inevitability of a final, bloody confrontation has grown amid Western outrage over attacks that killed hundreds over the weekend and which aid agencies said was making it impossible to help those people still being held by the rebels.
Analysts and diplomats said the end of voting in India's month-long election on Wednesday was likely to usher in an all-out attack by Sri Lanka to wipe out the Liberation Tigers of Tamil Eelam (LTTE) and bring a conventional end to a 25-year war.
The International Committee of the Red Cross, unable to ferry out wounded and deliver aid by boat because of days of fighting, said one of their local staff was killed.
"A 31-year-old local worker was killed this afternoon inside the conflict zone by shelling. His mother was also killed," ICRC spokeswoman Sarasi Wijeratne said. The ICRC is the only international aid agency working inside the war zone.
Wijeratne did not say who fired the shells.
The LTTE and military had no immediate comment.
Late on Tuesday, the Tigers used six boats to attack troops.
"Some of the cadres landed and we had a confrontation," military spokesman Udaya Nanayakkara said. Three suicide boats were destroyed, he said.
It is impossible to verify battlefield accounts, since the war is mostly off-limits to outsiders and both sides have distorted events to their advantage since war erupted in 1983.
THE INDIAN FACTOR
Sri Lanka's war has become a delicate election issue for India's ruling Congress party in the swing state of Tamil Nadu, home to 60 million Tamils across the Palk Strait where the LTTE was incubated and still commands support.
"I think the war was slowed down because India's politicians requested that to save some embarrassment for the ruling party in Delhi," said Col. R. Hariharan, the former intelligence head for the Indian Army's 1987-1990 peacekeeping mission in Sri Lanka.
A diplomat in Colombo, speaking on condition of anonymity, said: "This is it. After the election, they will go full-blast. Unfortunately, I think it will only make reconciliation harder. That is a waste of time."
Sri Lanka is eager to finish off the LTTE and avoid external intervention, which has saved the rebels from defeat earlier in their war to create a separate state for minority Tamils.
Human Rights Watch and Amnesty International on Wednesday said satellite photographs, given preliminary analysis by the American Association for the Advancement of Science, showed evidence of artillery shelling.
"Neither the Sri Lankan army nor the Tamil Tigers appear to have any reluctance in using civilians as cannon fodder," said Brad Adams, Asia director at Human Rights Watch.
The Tigers, all of whom are said to wear cyanide capsules to take in case of capture, have ruled out surrender altogether and refused to release an estimated 50,000 people in their area.
Sri Lanka has refused calls to declare another truce, and says it can rescue the remaining civilians as it did some 200,000 others who fled this year as troops seized separatist territory.
The military insists it has not used any heavy weapons for months, and pledged on April 27 to stop using them, an assertion the United Nations and others view with scepticism.
Nanayakkara said the craters in the photographs could have been caused by boobytraps which the LTTE laid while retreating.
The Tigers this week accused the government of killing hundreds of civilians while shelling a makeshift medical clinic from three days starting on Sunday. Both sides blamed the other. (For a related factbox, click on [ID:nCOL475616]) (Editing by Alex Richardson)