Baghdad  - A father and a son were killed Wednesday in a bomb blast in Iraq's restive Diyala province while Iraqi troops uncovered weapons caches in Baghdad's Sadr City district, the stronghold of the Mahdi Army militia.

A bomb went off on a main road linking Qura Tiba and Kafri near Baquba, 185 kilometres north-east of Baghdad, hitting a civilian vehicle, the Voices of Iraq news agency quoted a local official, Sirwan Shukr, as saying.

Two passengers in the car - a father and his son - were killed and another son was injured in the blast.

In Baghdad, Iraqi troops seized weapons caches in Sadr City, where troops have been deployed after months of heavy fighting with the Mahdi Army militia of radical cleric Moqtada al-Sadr, the US military said Wednesday.

The caches discovered Tuesday contained a rocket-propelled grenade launcher, a trigger device, explosives and mortar rounds as well as other types of ammunition.

Calm has returned to Sadr City after the enforcement of a truce deal between the government and al-Sadr. (dpa)