Oil workers' unions in Nigeria have threatened to withdraw members from the main oil-producing region unless the government moves to improve security.
Local people say they do not benefit from the oil wealth
The two main unions issued a statement saying oil workers were always the first targets of the aggression of young militants in the Niger Delta.
The unions condemned the recent kidnapping of four foreign workers during a raid on an oil station.
The hostage-takers say one of the captives, an American, is very ill.
The Movement for the Emancipation of the Niger Delta, the previously unknown group believed to be behind the kidnappings, reiterated a demand for compensation of $1.5bn from the Shell oil company for pollution in the Niger Delta.
The unions said 22 people had been killed since a militant attack on 11 January, when the four foreign oil workers were kidnapped.
"It needs to be mentioned that if the restiveness and consequent harassment and violence on workers in the oil and gas industry persist, we shall not hesitate to withdraw our members in the various oil and gas companies operating in the region," the Nupeng and Pengassan unions said in a joint statement.
Militants in the oil-rich Delta want local Ijaw people to benefit more from the region's oil wealth.
The hostage-takers are also demanding the release of separatist leader Mujahid Dokubu Asari, being held on treason charges, as well as former governor Diepreye Alamieyeseigha, accused of corruption and money-laundering.
The group attacked a Royal Dutch Shell pumping station near the port of Warri last weekend, prompting the oil giant to withdraw some 330 workers.
The instability has led to a 10% fall in Nigeria's oil production. The country is Africa's leading oil exporter and the fifth-biggest source of US oil imports.
The kidnappings are the latest in a string of violent incidents in the troubled region.