Nigeria's government has said it is reviewing all options in response to Islamic militant group Boko Haram's offer to trade the schoolgirls it abducted last month for jailed comrades.

It comes after Boko Haram released a new video claiming to show the missing Nigerian schoolgirls.

The group's leader Abubakar Shekau said the girls had converted to Islam.

He said they would not be released until all militant prisoners were freed.

Earlier, a Nigerian government minister was quick to reject the conditions set out by Shekau.

Asked if the government would reject the suggestion by Shekau in a new video that the girls may be released once Nigeria frees all militant prisoners, Interior Minister Abba Moro told AFP: "Of course."

"The issue in question is not about Boko Haram... giving conditions," he said.

At a news conference this afternoon Mike Omeri, director general of the National Orientation Agency, part of the Ministry of Information, said: "the government of Nigeria is considering all options towards freeing the girls and reuniting them with their parents." 

In the video, Shekau speaks for 17 minutes before showing what he said were about 130 of the girls.

They were wearing the full-length hijab and praying in an undisclosed rural location.

A total of 276 girls were abducted on 14 April from the northeastern town of Chibok, in Borno state. More than 220 are still missing.

Earlier, Nigerian President Goodluck Jonathan said international military and intelligence assistance made him optimistic about finding the schoolgirls.

Israel became the latest country to offer help to the Nigerian government.

Israeli Prime Minister Benjamin Netanyahu's office gave no details of its proposed assistance but Mr Jonathan said Mr Netanyahu offered to send a team of counter-terrorism experts.

The US and Britain have flown in experts and this, coupled with the deployment by Nigeria of two army divisions to the border region, signals that the search effort is gathering pace.

But it comes against a backdrop of sharp criticism of Mr Jonathan's government for responding too slowly to the crisis.

"Nigeria would be pleased to have Israel's globally acknowledged anti-terrorism expertise deployed to support its ongoing operations," the Nigerian government said.

Mr Jonathan is "very optimistic that with the entire international community deploying its considerable military and intelligence-gathering skills and assets in support of Nigeria's efforts ...  success will soon be achieved".

Meanwhile, the governor of Borno state has said he has information about where they are.

Governor Kashim Shettima said he did not think the girls had been taken across the border to Chad or Cameroon.

He said he has passed information on sightings of the girls to the military for verification.

Outrage over the attack has focused attention on Boko Haram, a group that has destabilised parts of northeast Nigeria and killed thousands since 2009 in its fight for an Islamist state.

French President Francois Hollande yesterday offered to host a summit in Paris next Saturday with Nigeria and its neighbours focused on the militant group.

"With Nigerian President Goodluck Jonathan, I have proposed to hold a meeting with the countries bordering Nigeria," Mr Hollande said.

The leaders of Benin, Cameroon, Chad and Niger might also attend and Britain, the European Union and the US would likely be represented as well, Mr Hollande's aides said.

A campaign on social media using the Twitter hashtag #BringBackOurGirls has stoked concern over the kidnappings, which have touched a chord because of the vulnerability of the girls and the brutality of the attackers.