Britain is prepared to send special forces and intelligence-gathering aircraft to Nigeria to help in the hunt for the schoolgirls abducted by Boko Haram militants, Whitehall officials have said.

Options for British support for the Nigerian forces struggling to find nearly 300 young girls were discussed by officials at a meeting of the government's emergency committee, Cobra.

The Foreign Office and the Ministry of Defence declined to say what help Britain might provide until the Nigerian authorities made an official request.

Details of the assistance that Nigeria requires are expected to be handed to Britain on Wednesday, though it is understood that unofficial talks between the two countries have already taken place.

The Nigerian president, Goodluck Jonathan, on Tuesday welcomed a US offer to send an American team to Nigeria to support its response to the kidnappings.

The US has operated a drone base in neighbouring Niger since 2012, but Africa's most populous country has long rebuffed requests for them to operate on its territory.

White House spokesman Jay Carney said that president Barack Obama has been briefed on the situation several times, and described the abductions as "an outrage." He said Washington was providing assistance in counter-terrorism training, including forensics and investigative capacity.

William Hague, the foreign secretary, said Britain was offering Nigeria assistance in recovering the girls who were being "treated as spoils of war by Boko Haram".

Senior government officials said special forces – members of the Special Air Service (SAS), or its naval equivalent, the Special Boat Service (SBS) – would be deployed in Nigeria if asked to do so.

One possibility for British military involvement is that experienced UK special forces troopers would be sent out to advise Nigerian special forces.

UK special forces are normally deployed in rescue missions when British citizens or residents are being held captive. The last time they were deployed to Nigeria was in 2012 when the SBS joined Nigerian soldiers in an attempt to save the lives of Chris McManus, a construction worker, and his Italian colleague, Franco Lamolinara. They were killed by Islamist kidnappers moments after the rescue mission was launched.

British officials also said that the RAF could send Istar (intelligence, surveillance, target acquisition and reconnaissance) planes to search for the children and their abductors.

Sentinel aircraft played a key role during the military operations over Libya three years ago. The aircraft can intercept communications as well as monitor movements on the ground.

All of Britain's Reaper unmanned aircraft are operating in Afghanistan though the US drones in Niger were deployed there during the crisis in Mali last year.

The US secretary of state, John Kerry, offered US support in a phone call to President Jonathan, who welcomed it, said state department spokeswoman Jen Psaki.

Kerry said Washington was "ready to send a team to Nigeria to discuss how the United States can best support" efforts to find the girls, Psaki added.

Washington had also offered to set up a coordination cell at their embassy in Abuja with US military personnel, law enforcement officials and experts in hostage situations, she said.

Boko Haram claimed responsibility for the abductions in a video obtained by Agence France-Presse on Monday.

Although the girls, aged between 16 and 18, were kidnapped from their boarding school in north-eastern Nigeria three weeks ago, the release of a video showing the leader of Boko Haram, Abubakar Shekau, threatening to sell the girls has pushed the abductions to the forefront of US television news.

US lawmakers have called on the Obama administration to do all it can to help free the girls, and a Twitter hashtag #BringBackOurGirls has gone viral.

About 200 protesters gathered on Tuesday outside the Nigerian embassy in Washington to demand the country take robust action to rescue the girls from the hands of the Islamist militants.

Chanting "bring back our girls" and "no more abuse," they called upon Jonathan to show what one speaker called the "testicular fortitude" to resolve the crisis.

'Craziest commander'

Dressed in green combat fatigues and standing in front of an armoured personnel carrier mounted with machine guns, Abubakar Shekau laughs as he informs viewers he plans to sell almost 300 girls kidnapped by his fighters. "Why is everybody making noise just because I took some girls who were in western education anyway?" he says, almost giggling, in the video which was released on Monday.

The rhetoric is typical of the Boko Haram's leader brash on-screen persona. Introduced to Boko Haram's previous leader, Mohammed Yusuf, who was killed in police custody in 2009, Shekau was one of a trio of theology students whose movement grew into the group whose name translates as "western education is wrong".

But little is known about Nigeria's most wanted man, who the US and UK designated a terrorist last year. The state department offered a $7m reward for information on his whereabouts – higher than the $5m offered for commanders of other regional al-Qaida affiliates such as the Mali-based al-Qaida in the Islamic Maghreb.

Screen grab of Abubakar Shekau. Photograph: AFP/Getty Images

Born in Shekau, an impoverished village in Yobe, one of north-east Nigeria's poorest states, he is believed to be aged between 40 and 45. He grew up in a simple mud-and-straw house typical of the area and studied at local Qur'anic schools before moving to Maiduguri, the capital of Borno state, Boko Haram's spiritual home.

A Boko Haram intermediary said Shekau was fastidious about his personal hygiene and rejected luxuries as a sign of weakness. Male visitors were sometimes berated for wearing trousers that reached below the ankles – which some Muslims consider an infringement of the Hadith, or sayings and deeds attributed to the prophet Muhammad. But his controlling personality meant his commanders deserted, and his dictatorial leadership prompted the breakaway Ansaru faction, according to a senior security official. Ansaru differed primarily in a desire to avoid killing Muslims, and were responsible for the 2011 kidnap and murder of a British and Italian hostage in Nigeria.

"He is the craziest of all the commanders. He really believes it is OK to kill anyone who disagrees with him – whether a child or a fellow Muslim. His own commanders are afraid of him," the intermediary said.

Nigeria's intelligence forces have variously boasted they have killed the leader of Boko Haram, only for him to appear. But analysts also believe Shekau has at least one double. A senior security official at Nigeria's counter-terrorism office said Shekau was badly injured in a series of air raids last year, and is believed to have retreated initially to Mali, then to Cameroon's Gwoza caves for recuperation.

Videos released by the group during this period showed a fresher-faced, younger-looking Shekau, although the rhetoric is as incendiary as ever. Monica Mark