NANGARHAR/KABUL (Reuters) - Five Afghan policemen died in a Taliban attack on a security checkpoint near a copper mine on Tuesday, officials in the region said, a day after the insurgents decided to resume operations against local forces.

A Taliban spokesman did not confirm or deny responsibility for the attack in eastern Afghanistan when contacted by Reuters, saying he was collecting information.

The militants had a reduction of violence arrangement in place before the signing of a troop withdrawal agreement with the United States in Doha on Saturday.

But on Monday they decided to end that for Afghan forces, while still holding back on fighting American and other foreign troops, according to sources.

Tuesday's "heavy clash" killing five Afghan officers took place at a checkpoint at the Mes Aynak copper mine in Logar province, said Deedar Lawang, a spokesman for Logar's provincial governor.

Hasib Stanekzai, head of Logar provincial council, told Reuters the policemen were soft targets during the early morning attack as they had no heavy weapons.

A senior U.S. official said the attack was being investigated.

A spokeswoman for Afghanistan's interior ministry said that in 24 hours, the Taliban carried out 33 attacks against Afghan forces in 16 provinces, killing six civilians. She did not say how many Afghan security force members had died.

"Taliban should give up killing civilians, otherwise (Afghan National Security forces) take action and eliminate them in the defence of our people," said the spokeswoman Marwa Amini.

U.S.-led forces ousted the Taliban from power in 2001.

But the nation has been in stalemate since, with Taliban forces controlling some territory but unable to capture major urban centres.

The weekend agreement envisages a full withdrawal of all U.S. and coalition forces within 14 months, dependent on security guarantees by the Taliban.

"If the announcement of resumption of violence by Taliban is verified, this is against the spirit of the agreement just signed in Doha," tweeted the European Union's special envoy for Afghanistan, Roland Kobia.