* Amnesty claims army had warning of attack
* Saudi Arabia grand mufti condemns Boko Haram
* US Senate committee to hold hearings over attack (Adds Amnesty, Nigeria defence, Interpol, US Senate committee)
By Matthew Mpoke Bigg
ABUJA, May 9 (Reuters) - Nigerian President Goodluck Jonathan said on Friday he believed 200 schoolgirls abducted by Islamist militants last month in an attack that has stirred global outrage are still in his country and have not been moved to neighbouring Cameroon.
As condemnation of the abductions spread, Saudi Arabia's grand mufti, the top religious authority in the birthplace of Islam, said Boko Haram rebels who conducted the abductions had "set up to smear the image of Islam".
Jonathan's government has been criticized for its slow response to the hostage crisis, and Friday is the first time he has said where he thinks the girls are being held.
"There are stories that they have moved them outside of the country. But if they move that number of girls to Cameroon, people will see, so I believe they are still in Nigeria," Jonathan told journalists.
"We are also working with the experts that will use remote sensors to see them (insurgents) wherever they are. So that basically says they are within the Sambisa area," Jonathan said, referring to a forest that is a known Boko Haram hideout near the school from where the girls were abducted.
He was speaking on the sidelines of the World Economic Forum in the Nigerian capital. The event showcased investment opportunities in Africa's biggest economy, but was partially overshadowed by the kidnapping and a broader militant threat.
Boko Haram's struggle for an Islamic state has killed thousands since it erupted in mid-2009 and has destabilized swathes of the northeast of Africa's top oil producer, as well as neighbours Cameroon and Niger.
Militants stormed a secondary school in the village of Chibok, near the Cameroon border, on April 14, and kidnapped the girls, who were taking exams at the time. Fifty have since escaped, but more than 200 remain with the insurgents.
Nigeria's military has struggled to maintain security in the turbulent northeast as Boko Haram grows bolder.
Human rights group Amnesty International said in a statement, citing multiple interviews with sources, that the security forces had been warned more than four hours in advance about the school attack but did not do enough to stop it.
"The fact that Nigerian security forces knew about Boko Haram's impending raid but failed to take the immediate action needed to stop it will only amplify the national and international outcry at this horrific crime," said Netsanet Belay, Amnesty's Africa director of research and advocacy.
Nigeria's Defence Headquarters spokesman Chris Olukolade dismissed Amnesty's report as baseless and said it was aimed at tarring the reputation of the country's authorities.
"The report is just a collation of the rumours, views and allegations of their fellow detractors and local operatives," he said.
Saudi Arabia's grand mufti Sheikh Abdulaziz Al al-Sheikh said Boko Haram had been "misguided" and should be "shown their wrong path and be made to reject it."
His remarks came as religious leaders in the Muslim world, who often do not comment on militant violence, joined in denouncing Boko Haram leader Abubakar Shekau for saying Allah had told him to sell off the kidnapped girls as forced brides.
Jonathan on Thursday thanked countries including the United States, Britain, France and China for their support in trying to rescue the girls. All have offered assistance. International police agency Interpol on Friday also offered its help.
British experts including diplomats, aid workers and Ministry of Defence officials arrived in Nigeria on Friday to advise the government on the search.
The Senate Foreign Relations Subcommittee on Africa Affairs said it will hold a hearing next Thursday on U.S. offers of assistance to Nigeria after the abductions.
The revolt has displaced more than 250,000 people in Nigeria and 60,000 have fled the country, U.N. refugee agency (UNHCR) spokesman Adrian Edwards said in Geneva on Friday. UNHCR is "alarmed at the recent wave of attacks on civilians", he said.
A militant attack on the market town of Gamburu early on Monday killed at least 125 people, police said. (Additional reporting by Tim Cocks and Chijioke Ohuocha in Abuja, Lanre Ola in Maiduguri, Tom Miles in Geneva, Andrew Callus in Paris, Sami Aboudi in Dubai, Patricia Zengerle in Washington and Guy Faulconbridge in London; Editing by Janet Lawrence)