Zimbabwe's President Robert Mugabe acknowledged Friday he had suffered an electoral disaster in losing a first round against arch rival Morgan Tsvangirai, as the date for a run-off was fixed for June 27.

In his first detailed comments since losing a joint presidential and parliamentary election on March 29, Africa's oldest leader lambasted his party and also accused the opposition of embarking on a campaign of terror.

Tsvangirai meanwhile said he was confident of winning the run-off and his Movement for Democratic Change (MDC) party said he would return home on Saturday to begin a final push for power after more than a month out of the country.

The 84-year-old Mugabe, who has ruled the former British colony since independence in 1980, won 43.2 percent of votes against 47.9 percent for Tsvangirai in the first round and in theory is now the underdog.

With his Zimbabwe African National Union - Patriotic Front (ZANU-PF) party having also lost control of parliament, Mugabe made no attempt to disguise his fury at the outcome as he addressed its central committee.

"Although the presidential result did not yield an outright winner it was indeed disastrous," he said.

"Fundamentally we went to the election completely unprepared, unorganised ... As leaders we all share the blame, from the national level to that of branch chairman.

"Nevertheless we are set for a second round, for the run-off which must now decide the winner."

The period since election day has been marked by increased violence and the opposition says more than 30 of its supporters have died at the hands of Mugabe followers.

In a report this week, the senior UN representative in Zimbabwe said while both parties had been guilty of attacks, ZANU-PF were the main perpetrators.

However Mugabe blamed the opposition, accusing its supporters of "visiting terror on villages and (ZANU-PF) party supporters".

"The MDC and its supporters are playing a very dangerous game. They should know they cannot win that kind of war which they have carried to rural constituencies in the hope of destabilising our supporters."

Tsvangirai said he wanted to return home as a show of solidarity with supporters who have been targeted by Mugabe's followers.

"It is because of these people that I must return to Zimbabwe, to be with our people, to lift them out of this darkness that pervades their lives," he said in a speech on a visit to Northern Ireland.

Tsvangirai said the violence would not prevent him from winning the run-off.

"Mugabe lost that first round, 57 percent of the people who cast their vote did not vote for him.

"I am so confident that in spite of the violence, come the second round they will reconfirm that rejection."

MDC spokesmen said Tsvangirai would return Saturday and immediately kick off his run-off campaign.

He would first address MDC lawmakers in Harare before heading to the main southern city of Bulawayo to address a rally.

"The rally in Bulawayo will mark the beginning of nationwide rallies in which he will be seeing victims of political violence as well as thanking the nation for voting for change on March 29," MDC director of information Luke Tamborinyoka told AFP.

Tsvangirai, who only reluctantly agreed to take part in the run-off as he believes he passed the 50 percent threshold in the first round, has previously demanded the ballot be held by May 23 in line with the electoral law.

However the electoral commission confirmed on Friday that the deadline would be missed and instead set the run-off for the end of next month.

In a notice placed in an extraordinary government gazette, the commission announced that "a poll shall be taken on Friday, June 27, 2008, for the purpose of electing a person to the office of president."

Seen as a post-colonial success story in the first decade-and-a-half after independence, Zimbabwe's economy has been in freefall since 2000 when the 84-year-old Mugabe embarked on a land reform programme which saw thousands of white-owned farms expropriated.

Eighty percent of the workforce is unemployed while the official inflation rate in February stood at 165,000 percent -- the highest in the world.