LONDON (Reuters) - The widows of four of nine men executed by Nigeria’s military regime in 1995 have filed a civil lawsuit seeking compensation and an apology from Royal Dutch Shell for alleged complicity in a military crackdown, according to a writ filed in a court in The Hague.

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The Nigerian military cracked down heavily on local opposition to oil production by a Shell joint venture in the Niger Delta in the early 1990s. The four widows allege that Shell provided support to the military in the crackdown that ultimately led to the executions of the men, known as the Ogoni 9.

Shell, the largest oil producer in Nigeria, has repeatedly denied any involvement in the executions or the government’s response to the unrest.

“We have always denied, in the strongest possible terms, the allegations made by the plaintiffs in this tragic case,” Shell said in a statement.

“SPDC (Shell Petroleum Development Company of Nigeria) did not collude with the authorities to suppress community unrest and in no way encouraged or advocated any act of violence in Nigeria. In fact, the company believes that dialogue is the best way to resolve disputes.”

In 2009, Shell agreed in an out-of-court settlement in the United States to pay $15.5 million in damages to a group of relatives of the nine.

The four widows’ civil case was filed by human rights lawfirm Prakken d’Oliveira with the support of Amnesty International on behalf of Esther Kiobel, Victoria Bera, Blessing Eawo and Charity Levula. The writ did not specify how much compensation they were seeking.

“Shell and the military regime formed an alliance in the events leading to the deaths of the Ogoni 9,” the writ said.

“Their relationship was one of mutual dependence: the Nigerian state was dependent on the income from oil that Shell generated; in turn, Shell was dependent on the benevolence and protection of the regime to pursue its activities in Nigeria and in this way realize a substantial part of its turnover.”

Kiobel previously took a lawsuit to the United States but the U.S. Supreme Court ruled in 2013 that the case could not be heard because the country did not have jurisdiction.

A number of groups have pursued in recent years cases against Shell in courts in the United Kingdom, the United States and the Netherlands over claims related oil spills and environmental damage, claiming they cannot get a fair hearing in Nigeria.