HARARE, Zimbabwe — Zimbabwe’s longtime ruler Robert Mugabe was sworn in as president for a sixth term today after a widely discredited runoff in which he was the only candidate. His main rival dismissed the inauguration as “an exercise in self-delusion.”

Just hours after electoral officials said Mr. Mugabe won Friday’s presidential runoff, which observers said was marred by violence and intimidation, the 84-year-old leader sounded a conciliatory note.

“Sooner or later, as diverse political parties, we shall start serious talks,” he said in a speech following his swearing-in. He also had promised talks on the eve of the vote.

Mr. Mugabe, Zimbabwe’s leader since independence from Britain in 1980, was expected at an African Union summit that opens tomorrow in Egypt, where he was to face fellow African leaders who want him to share power with his main rival, Morgan Tsvangirai.

Mr. Tsvangirai, leader of the opposition Movement for Democratic Change, said that today’s inauguration was “meaningless.”

“The world has said so, Zimbabwe has said so. So it’s an exercise in self-delusion,” he said.

Mr. Tsvangirai said he believed members of Mugabe’s ZANU-PF party were ready for talks.

“I think that the reality has dawned on all the elites in ZANU-PF,” Mr. Tsvangirai said. “Without negotiating with the MDC this is a dead-end.”

African and other world leaders have condemned Friday’s vote. Human rights groups said opposition supporters were the targets of brutal state-sponsored violence during the campaign, leaving more than 80 dead and forcing some 200,000 to flee their homes.

Residents said they were forced to vote by threats of violence or arson from Mugabe supporters who searched for anyone without an ink-stained finger — the telltale sign that they had cast a ballot.

Today, Human Rights Watch said in a statement that Mugabe supporters beat people who couldn’t prove they voted.

Mr. Tsvangirai withdrew from the race because of the violence, though his name remained on the ballot and his supporters may have spoiled their ballots rather than vote for Mugabe.

The electoral commission said total results showed more than 2 million votes for Mr. Mugabe, and 233,000 for Mr. Tsvangirai. Turnout was put at about 42%, and 131,000 ballots had been defaced or otherwise spoiled, apparently as an act of protest. Neither candidate got credit for the spoiled ballots.

In the opposition stronghold of Bulawayo, official results showed Mr. Mugabe got 21,127 votes and Mr. Tsvangirai had 13,291, while 9,166 ballots were spoiled.

A high number of spoiled ballots had been noted earlier today by a member of parliament from Swaziland, Marwick Khumalo, who led a team of election observers from across the continent under the auspices of the AU-sponsored Pan-African Parliament.

Mr. Khumalo said some ballots were defaced with “unpalatable messages.” He refused to elaborate, but left the impression the messages expressed hostility toward Mr. Mugabe, who has been accused of ruining Zimbabwe’s economy and holding onto power through fraud and intimidation.

Mr. Tsvangirai won the most votes in the first round of presidential voting in March, but not enough for an outright victory. Official results were not released for more than a month after that vote.

In recent days, African mediators have been pushing for Messrs. Mugabe and Tsvangirai to negotiate a power-sharing agreement.

Mr. Mugabe said on the eve of Friday’s vote he was open to talks, but pressed ahead with the election, apparently hoping a victory would give him leverage at the negotiating table. It now appears he will be able to draw little legitimacy from the runoff.

Mr. Khumalo, the observer, urged African and regional leaders to “engage the broader political leadership in Zimbabwe into a negotiated transitional settlement.”

With the election discredited and attention turning to the possibility of negotiations, Mr. Mugabe’s role in any future government could be a sticking point.

Mr. Tsvangirai said in an interview with The Sunday Telegraph of Britain that Mr. Mugabe might be allowed to stay on as ceremonial president of a transitional government, with himself as executive prime minister.

“It’s being considered within our structures,” the paper quoted Mr. Tsvangirai as saying.

Also today, an American-led push to punish Zimbabwe ran into resistance from China, which can veto U.N. penalties sought against its African ally.

After talks with Secretary of State Rice, China’s foreign minister said Beijing favors negotiations between Mr. Mugabe and the opposition.

“The most pressing path is to stabilize the situation in Zimbabwe,” the foreign minister, Yang Jiechi, told reporters at a news conference with Ms. Rice. “We hope the parties concerned can engage in serious dialogue to find a proper solution.”

President Bush said yesterday America was working on ways to further punish Mr. Mugabe and his allies. That could mean steps against his government as well as additional restrictions on the travel and financial activities of Mugabe supporters. America has financial and travel penalties in place against more than 170 citizens and entities with ties to Mr. Mugabe, the White House says.

Mr. Bush also wants the U.N. Security Council to impose an arms embargo on Zimbabwe as well as travel bans on Zimbabwe government officials.

Ms. Rice has said America plans to introduce a resolution in the council this coming week. America holds the council’s presidency until July 1, but appears to face an uphill battle in getting several important members to agree to any penalties.

In addition to China, both Russia, also a permanent veto-wielding council member, and elected member South Africa have opposed action on Zimbabwe, saying the situation is an internal matter.

Mr. Mugabe was once hailed as a post-independence leader committed to development and reconciliation. But in recent years, he has been accused of ruining Zimbabwe’s economy and holding onto power through fraud and intimidation.

The official inflation rate was put at 165,000% by the government in February, but independent estimates put the real figure closer to 4 million%.

Since the first round of elections, shortages of basic goods have worsened, public services have come to virtual standstill, and power and water outages have continued daily.