Sri Lankan forces threw a security blanket over the capital Colombo yesterday and appealed for extra public vigilance a day after twin bomb attacks left 19 people dead and 45 injured, police said.
"There is a general security alert across Colombo," police spokesman Jayantha Wickremaratna said.
Officials have blamed the bombs on Liberation Tigers of Tamil Eelam (LTTE) rebels, saying they were targeting civilians in revenge for military defeats.
"In the midst of repeated defeats and setbacks in the battlefield, LTTE attacks against civilians could intensify in the coming weeks," Wickremaratna said.
"The LTTE has targeted innocent civilians who have no involvement in the ongoing military operations," he said.
England's cricket test series in Sri Lanka would go ahead despite the attacks, team spokesman Andrew Walpole said.
Thirty-three people remain in hospital after a powerful parcel bomb exploded at Nugegoda, just south of Colombo, killing at least 17 and injuring 43 during Wednesday's evening rush hour, police said.
Earlier Wednesday, a disabled Tiger suicide bomber with explosives hidden in her bra blew herself up outside the office of Social Services Minister Douglas Devananda, killing his secretary and wounding two security men.
Schools in and around Colombo were closed yesterday for two days as a "safety measure" while troops were on the streets manning roadblocks and checking motorists driving into the capital during the morning rush-hour.
"The general public should be extra vigilant about their surroundings in trains, buses, crowded areas and even in schools," Wickremaratna said.
Police also banned vehicles from entering the plush twin-tower World Trade Center that houses the Colombo Stock Exchange and several ministries.
Meanwhile, London-based Amnesty International criticized the Tamil Tigers yesterday for attacking civilians, saying the attacks violated international humanitarian law.
"The LTTE must stop any direct or indiscriminate attacks on civilians," Amnesty secretary-general Irene Khan said.