Supporters of Zimbabwe President Robert Mugabe raise a flag during an election rally for the ruling ZANU PF party's youth Friday in Harare, Zimbabwe.

Harare, Zimbabwe ? President Robert Mugabe said Friday that his supporters are ready to fight if the opposition wins an upcoming presidential runoff election, hardening the rhetoric of a campaign that already has seen widespread violence against government opponents.

“I’m even prepared to join the fight,” the 84-year-old Mugabe told a conference of his party’s youth wing.

Mugabe said the veterans of the war of independence in 1980 had approached him after the first round of voting in March and threatened to take up arms again if opposition leader Morgan Tsvangirai wins the June 27 runoff.

Tsvangirai finished first in a field of four in the first round but failed to win the majority needed to avoid a runoff.

“We can’t allow the British to dominate us through their puppets,” said Mugabe, returning to a campaign theme of portraying Tsvangirai as a pawn of Western powers, a charge the opposition denies. “A vote for the (opposition) is a vote for the British to have once again not just a foothold but real power.”

A High Court judge, meanwhile, ordered police to bring No. 2 opposition leader Tendai Biti to court today and explain why he should not be immediately released, according to opposition lawyer Selby Hwacha.

Biti was arrested Thursday upon returning to Zimbabwe from neighboring South Africa. The United States was among the governments that said the arrest of the top aide to Tsvangirai only deepened concerns the runoff would not be free and fair.

Since picking up Biti at the airport Thursday, police have refused to say where he was being held or when they might bring him to court. They have said he faces a charge of treason, which can carry the death penalty.

Tsvangirai, speaking on the campaign trail, called the charge Biti faces “frivolous.”

“Tendai has not committed any crime, he has not committed any offense to warrant the arrest,” the candidate said.

The party said Tsvangirai himself was released overnight after being detained by police.

Tsvangirai was stopped twice by police as he tried to campaign Thursday, according to the party, which said he was held for about two hours the first time and late into the night the second time before being released. Such incidents have become common as Tsvangirai attempts to reach out to voters, and the opposition says 66 of its supporters have been killed.