Shell has started to move the families of its staff out of the oil-producing Niger Delta region of Nigeria. This follows a bomb explosion on Monday in an area where they live. On Thursday morning, Total, a rival oil company, was also attacked. The BBC's James Copnall reports from the area:

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Monday's attack, which also targeted the Italian oil firm Agip, was the work of the Movement for the Emancipation of the Niger Delta, or MEND. Early on Thursday morning there was an attack on a third oil company, Total. Reports say that three police officers guarding an oil facility were killed but no hostages were taken. The identity of the attackers is not yet clear.

Militant groups and common criminals frequently attack oil companies and kidnap foreign staff in the oil-rich Niger delta. MEND kidnapped three Italians and a Lebanese citizen earlier in the month and is still holding them. MEND and some other groups say they are fighting for a fairer share of oil resources. The oil from the Niger delta makes Nigeria the world's twelfth biggest producer but the region remains extremely poor.

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a precautionary measure
something that's done to try to stop something dangerous or unpleasant from happening

casualties
deaths or injuries

'under the tip of our noses'
very close, near by

residential compound
an enclosed area built for people to live in

confident
sure

targeted
specially chose, was aimed at

hostages
people who have been taken away by force and kept as prisoners until the demands of the people who took them are met

identity
details of who they are, e.g. name, address and nationality

kidnap
forcefully and illegally take someone away and hide them in order to get money when they are released

oil resources
oil supplies that are available in their country

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