* Government at pains to show it can stamp out insurgency

* Islamists targeting Abuja with bombs on petrol lorries

* Ten Boko Haram members killed in northeast (Recasts, adds killing of 10 militants)

By Camillus Eboh

ABUJA, June 19 (Reuters) - Islamist militants are planning to attack Nigeria's capital with bombs loaded on petrol lorries, the Nigerian government said, stoking fears of a sustained push to the south from their northern heartland.

Abuja is at pains to show it can crush Boko Haram's insurgency since the group drew worldwide attention in April by abducting more than 200 girls from a school in the northeast.

On Thursday, the government said - as evidence it was pushing back - that security forces had killed 10 of the group's members in northeast Borno state, marking a rare recent success.

Without saying how the government planned to counter the attacks, a senior information ministry official, Mike Omeri, said in a statement late on Wednesday that the insurgents were planning to plant "improvised explosive devices in the tankers and drive them to crowded places in Abuja".

Boko Haram has killed thousands since 2009 and says it wants to create an Islamic state in Nigeria's mostly Muslim north.

Two bomb blasts in the central capital of Abuja in the south in the weeks running up to the World Economic Forum in the capital in May killed more than 90 people and prompted some delegates to pull out of the conference.

Security forces this week discovered a senior Boko Haram member among a convoy of nearly 500 travellers in the southern state of Abia.

The presence of a high-ranking militant in the mainly Christian south has raised concern that Boko Haram could eventually attempt attacks in the oil-producing Niger delta.

Police in the southern state of Imo, in the eastern part of the delta, defused three bombs found at a Christian church over the weekend. Six people have since been arrested. (Additional reporting by Isaac Abrak; Writing by David Dolan; Editing by Louise Ireland)