Britain is working urgently to decide what technical and financial help it could provide to Lebanon after a massive blast ripped through Beirut killing at least 100 people.

"The government is working urgently this morning on what we can do to help the Lebanese government with technical support and of course working with our allies to provide financial assistance," British junior education minister Nick Gibb told BBC radio.

"There will be further announcements this morning and later today about what support we will be providing to Lebanon," Gibb said.