KABUL, Afghanistan –  An Afghan official says that five police officers including a district police chief have been killed when insurgents attacked their vehicle in the country’s west.

Raouf Ahmadi, spokesman for the provincial police chief of Herat province, said on Monday that Sher Ahmad district police chief and four other policemen were killed in the attack carried out in Herat’s Farsi district. Another officer was wounded, he says.

No group has claimed responsibility for the attack.

The violence comes as the Taliban have stepped up attacks against Afghan security forces ahead of results expected this week in the second round of the country’s contested presidential elections.