Three Afghan children were killed yesterday by a mortar left over from a battle between police and Tali ban, as bomb attacks and clashes left 31 more people dead, most of them insurgents, officials said.

There has been a steady increase in attacks and dashes across Afghanistan in recent weeks as US military reinforcements move into the south and Afghan forces target insurgent hotspots ahead of August 20 presidential elections.

The children, aged four to 10, were killed Fnday when they touched a mortar shell left over from an exchange of fire the previous day between Taliban and police in the central province of Ghazni, police said.

Another child was wounded, said provincial police chief Khial Baz Sherbaz.

Two roadside bombs exploded an hour apan in separate areas of the eastern province of Nangarhar on Friday, killing six policemen, provincial government spokesman Ahmad Zia Abdulzai told AFP.

Also in Nangarhar, a man was killed late Thursday by a bomb he was trying to plant inside a university faculty, the official said.

No one claimed the responsibility for the

bombings. Most of the almost-daily bomb blasts in the country, however, are linked to an insurgencybeing waged by the extremist Taliban, who were in government from 1996 to 2001.

Heavy fighting erupted in the troubled eastern province of Khost when militants attacked a compound where foreign troops were based, police said.

Ihe bodies of 15 militants remained at the site in the Sabari district, said the area's counterterrorism chief, named only Ghazoddin.

A policeman and a militia soldier contracted to the US military were also killed, he said.

The international forces sent attack helicopters to the battle, he said.

A Taliban spokesman confirmed the militia was involved, saying 100 men had attacked the district.

Meanwhile, police killed three Taliban militants in the neighbouring province of Paktya overnight, the provincial government said.

Separately, the US military said troops rounded up seven men with suspected ties to Taliban operations in the volatile southern province of Helmand, Afghanistan's number one opium producer.