RAMADI, Iraq, April 29 (Reuters) - Gunmen set fire to 15 fuel trucks heading to the Iraqi volatile province of Anbar on Sunday and kidnapped all the trucks' drivers, police said. Major Abdulghani al-Dulaimi said the trucks were transporting fuel from the Baiji refinery, north of Baghdad, to western Anbar. The incident happened early morning on a main road near Samarra, 100 km (60 miles) north of Baghdad. Insurgents frequently attack the country's oil and gas infrastructure. Anbar is a stronghold of the Sunni Arab insurgency and al Qaeda in Iraq.