Philippine President Gloria Arroyo has admitted a fresh wave of kidnappings has dealt a blow to the government's pledge to crack down on crime.

Over the past four days, gunmen have snatched two children of a wealthy congressman in Manila, the wife of a businessman in the north, and four university teachers in the south.

"It's a setback to our campaign," said Mrs Arroyo's spokesman Ignacio Bunye on Monday.

President Arroyo has given the police an ultimatum to crush 21 major kidnapping gangs within one year or face the sack.

She and members of her cabinet have been recently photographed dressed up as the tough characters from the comedy film Men in Black but critics say her bark is worse than her bite.

Children snatched

Kidnapping for ransom has become common in the Philippines in recent years, and is blamed for scaring away investors and tourists.

In the most prominent of the recent cases, gunmen on Friday snatched two children of House of Representatives member Julio Ledesma while they were being driven to school.

Police have stopped giving information to the media about the kidnapping for fear of endangering Carlos Tomas, aged five, and Cristina, 10.

However, Philippine newspapers are reporting that the kidnappers have demanded a $1m (60 million peso) ransom.

On Saturday an American teenager was released after his family paid his kidnappers $24,200 (1.25m pesos).

Starlze Lumapas, 15, was left unharmed by a roadside near the southern city of Cagayan de Oro, said police chief Superintendent Felicisimo Kho.

The boy, the son of Filipino-Americans based in Florida, in the US, was snatched from a relative's home near Cagayan de Oro last Tuesday as he was getting ready for school.

Police defend progress

Kidnappers have also demanded a ransom of $38,290 (2m pesos) for four university teachers snatched in the southern city of Marawi, officials said on Sunday.

The teachers were abducted from the campus of the Mindanao State University on Friday, by a gang allegedly made up of former university security guards.

And on Saturday, the wife of a car dealer in the northern city of Dagupan was kidnapped from a family-owned hardware store, police said.

Despite the rash of kidnappings, national police spokesman Senior Superintendent Reynaldo Bataoil insisted the police were making progress.

"If you go by percentages, there has been a 31% decline [in kidnapping incidents]" he said on television.

"But of course, just one high-profile kidnap for ransom case will negate all these accomplishments."