By Alexis Akwagyiram
Security experts say it is often best for a company to move employees
Four foreign oil workers have been kidnapped by militants in Nigeria.
BBC News asks what steps can be taken to protect people working in dangerous areas.
Shell has decided to review the deployment of its staff following a spate of attacks on workers based in the Niger Delta.
After four foreign workers - from the UK, US, Bulgaria and Honduras - were taken hostage by armed men in speedboats just over a week ago, the multi-national company is trying to reconcile oil production with the safety of its workers.
Nigeria is the world's eighth largest oil exporter and the biggest in Africa. Last year crude exports averaged around 2.6m barrels per day.
But Nigeria can be a particularly volatile environment for foreign workers.
On Wednesday the militant group Movement for the Emancipation of the
Niger Delta said that it would attack all oil companies in Nigeria and that its aim was to stop Nigeria's oil exports.
It said: "Pipelines, loading points, export tankers, tank farms,
refined petroleum depots, landing strips and residences of
employees of these companies can expect to be attacked.
"We know where they live, shop and where the children go to school."
When faced with such threats, what can a company do to combat any threat to its workforce?
The first step taken by Shell was to re-consider where its staff would work.
In a statement, the company said: "We continue to monitor developments in the western area of our operations in the Niger Delta and are taking necessary measures to ensure the safety and security of staff and contractors and the communities in which we operate.
"We continue to keep staff deployment in the western Niger Delta under close review. The safety of our staff, contractors and the communities in which we operate is our top priority and we will deploy staff as conditions dictate.
"We will also return to areas evacuated when normality is restored."
But it is clear from the Foreign Office's travel advice concerning Nigeria that foreign workers are at particular risk in the country.
It points out that seven oil workers - two US and five Nigerian - were killed in an attack on their boat in April 2004.
And the advice, on the Foreign Office website, goes on: "Hostage taking for ransom has occurred in Delta, River and Bayelsa States. Local youths have occupied oil facilities, including offshore rigs, to extort money from oil companies.
"Demonstrations and outbreaks of localised civil unrest and violence can occur with little notice throughout the country."
Violent incidents have slashed Shell's production in Nigeria by some 220,000 barrels a day - almost 10% of the country's average output.
Many companies employ risk assessors in a bid to combat any threat to staff.
Tara O'Connor is one such expert.
Ms O'Connor, who works in Africa for risk assessment firm Kroll, said many oil installations are difficult to protect because they are in isolated areas and local police are overstretched.
She said: "In high risk areas there is quite a corporate responsibility to ensure the safety and security of individuals.
"Most companies that operate in the Niger Delta have sophisticated security programmes, most of which involve moving workers who are at risk in certain areas.
Nigeria is one of the biggest oil producers in the world
"And the best advice that you can give to an individual is to make sure that before they go they get a security briefing so that they are aware of the risks to expect."
But not everyone heeds this advice, according to Norman Hoppe, a consultant who has worked in Nigeria.
"The biggest problem where there are expats from comfortable countries is that many suffer from 'it won't happen to me syndrome'.
"There is a tendency to view those giving advice as melodramatic and reject what they say."
He said many expats fail to heed advice until it is too late or they have either fallen foul of crime themselves, or those close to them have been robbed violently.
But Mr Hoppe had words of reassurance for westerners intending to relocate to countries which were struggling to cope with civil unrest.
"The advice is very simple and straightforward: heed the advice from people about places that are not safe to go, be alert and use common sense in decision-making."