Wickremsinghe had left the meeting about 30 minutes before the explosion reported to have been caused by a grenade that was flung into the crowd about 400 metres from the dais. A party MP was addressing the gathering at the time.

Party officials said that the grenade was meant for Wickremesinghe, but his departure from the meeting earlier than scheduled had foiled the attackers plans.

"Since his nomination by the party as their candidate, the Inspector-General of Police has strengthened his security, but it is not sufficient. We will be asking for more," said party general secretary Gamini Athukorale at a press conference on Monday.

Party spokesman Karunasena Koditawakku said it was"nowhere near" what President Chandrika Kumaratunga was provided by the UNP government when she stood for election in 1994.

Wickremesinghe had last week told this newspaper that he was satisfied with the security that the government had provided him since his candidature was announced, and said he felt "quite secure". But Sunday's incident may have cast a different light on the matter. Meanwhile, a special team of police officers is to probe the explosion that killed a 17-year-old student and a policeman, and injured 35 others.

UNP officials accused the ruling People's Alliance coalition of trying to disrupt the meeting, and said the explosion followed an argument between UNP workers and a group of people who were tearing down party posters.

The state-run daily Observer quoted a PA source as saying that the police had been asked to bring the culprits to book "irrespective of party allegiance".