LAGOS, July 7 (Reuters) - Lawyers for a leading Nigerian oil-region militant will seek an adjournment in his trial for treason and gun-running on Monday while they pursue an appeal to have the case heard in public, one of his legal team said.

Henry Okah is widely believed to be the leader of the Movement for the Emancipation of the Niger Delta (MEND), a militant group whose campaign of sabotage has cut Nigeria's oil output by around a fifth since early 2006, helping drive up world prices.

Okah still commands loyalty from several armed factions in the delta and Nigeria has said his trial at a federal court in the central city of Jos must be held behind closed doors for the sake of national security.

But the secrecy has angered his supporters.

An appeals court has accepted Okah's right to appeal to have the case heard in public and has asked his legal team to file written briefs in the next three weeks. It has said it will consider the appeal in September, according to Okah's lawyers.

"We will seek an adjournment for us to take up our appeal," one of Okah's lawyers, Wilson Ajuwa, told Reuters shortly before the main trial was due to resume on Monday.

"They (the prosecution) want to prevent us from appealing and we are objecting to that very strongly," he said.

He said the number of charges against Okah had also been increased for the fourth time, to 62 counts from a previous 55.

Okah could face the death penalty if convicted.

MEND has made Okah's release a condition for suspending its campaign of sabotage and for taking part in peace talks planned by the government of President Umaru Yar'Adua. (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/ ) (Reporting by Nick Tattersall, editing by Randy Fabi)

AlertNet news is provided by