Britain, Belgium, and Denmark have joined the U.S.-led coalition of nations that are launching air strikes on the Islamic State (IS) extremist group in Iraq.
After a seven-hour debate in the House of Commons on September 26, British lawmakers voted for military action by 524 votes to 43.
Six Cyprus-based Tornado jets are reportedly on standby to take part in initial strikes.
Reports said the planes could be called into action as early as September 28.
Prime Minister David Cameron told legislators in his opening address that intervention is "morally justified" to combat an organization that has shown "staggering brutality."
He also warned that the fight against its militants "could take years."
The beheading of two U.S journalists and a British aid worker by an IS militant with a British accent have galvanized public opinion against the Islamist group, which controls a patchwork of areas in Syria and Iraq.
Britain says some 500 of its citizens have gone to fight in the two countries, raising concerns some could return and carry out terrorist attacks in the United Kingdom.
Earlier on September 26, Belgian lawmakers also overwhelmingly approved the country’s participation in the aerial campaign against IS fighters in Iraq for one month.
Further involvement is to be subject to parliamentary evaluation and review.
Defense Minister Pieter De Crem said six F-16 fighters, to be based in Jordan, are to take part in the operation.
In Denmark, Prime Minister Helle Thorning-Schmidt said her government would contribute seven F-16 aircraft for 12 months to help combat IS militants in Iraq.
Danish lawmakers must approve the country’s intervention, but that is considered a formality.
"No one should be ducking in this case" Thorning-Schmidt said. "Everyone should contribute."
The United States began a series of air strikes against IS targets in Iraq in August, and this week began attacks in Syria.
British, Belgian, and Danish air force would join warplanes from the United States, France, and several Arab countries hitting IS targets.
No European country has yet agreed to strike in Syria.
Baghdad Hails Anti-IS Coalition
Addressing the United Nations General Assembly later on September 26, Iraqi President Fuad Masum applauded the U.S.-led international coalition supporting his country against IS militants.
Masum also called for greater regional cooperation against the extremist group which "thrives on crises and disputes."
He said the IS group, which controls large parts of northern and western Iraq, transcends states and continents.