Mr Tsvangirai says he won the presidential poll
The party of Zimbabwe's President Robert Mugabe has failed to regain its parliamentary majority after a partial recount of votes from polls last month.
Zimbabwe's Electoral Commission said results were unchanged in 18 of 23 seats where recounts had taken place.
Mr Mugabe's Zanu-PF needed to win nine seats to regain its majority, lost for the first time since 1980.
The opposition MDC says it also won presidential polls, although those results remain unreleased.
The Zimbabwe Electoral Commission (ZEC) said the presidential results could be announced after the completion of the recounts, expected by Monday.
But ZEC Chairman George Chiweshe said a "verification and collation" process would take place with agents of the presidential candidates before the long-awaited results were released.
HAVE YOUR SAY
It is obvious that Mugabe has lost the presidency
Brian, Kuala Lumpur
MDC spokesman Nqobizitha Mlilo told the BBC the recount results "only serve to confirm what we've always said in the past, that... we won this election hands down".
Deputy Information Minister Bright Matonga told AFP news agency that the recount results showed the electoral system was "transparent".
Opposition activists had feared the recount would be used to rig the results.
The BBC's Peter Biles in Johannesburg says the protracted recount of votes has given Zanu-PF a lot of extra time in which to decide how to deal with what the opposition says is a defeat for Robert Mugabe.
The MDC says its leader, Morgan Tsvangirai, won the presidential election outright, while independent monitors say he fell just short of the 50% threshold to avoid a run-off.
Zanu-PF also says there is likely to be a run-off, as no candidate gained more than 50% of the vote.
The MDC has alleged a government campaign of intimidation
The government has been accused of inciting an increasing campaign of violence against opposition supporters.
Lawyers have told the BBC they have been denied access to about 185 MDC supporters still in custody after raids on the opposition party's Harare office and the headquarters of an independent monitoring network on Friday.
Police said they had initially arrested 215 people suspected of involvement in political violence.
But the MDC said some of those detained had been taking refuge from attacks by ruling party activists in other parts of the country, and told the Associated Press news agency they included pregnant women and men with broken bones.
Reports said none of those arrested had been charged.
The same day, the US-based group Human Rights Watch said Zanu-PF and state security forces had "sharply intensified a campaign of organised terror and torture against opposition activists and ordinary Zimbabweans".
The MDC says at least ten of its activists have been killed around the country, although the police and Zanu-PF say no-one has died in political violence.
On Saturday, a group of churches in the second city of Bulawayo said it was opening its doors to "shelter the victims of harassment".
US Assistant Secretary of State Jendayi Frazer, touring the region to tackle the post-election crisis, said the level of government intimidation in Zimbabwe was now so high that a fair run-off would not be possible.
She said the only solution was an inclusive government, led by the opposition Movement for Democratic Change.
Zimbabwe Justice Minister Patrick Chinamasa called her comments "patently false, inflammatory, irresponsible and uncalled-for".
UK Prime Minister Gordon Brown said he was concerned about "worsening violence" in the country and pledged to step up diplomatic efforts at the UN Security Council in the coming days.
Four elections - presidential, House of Assembly, Senate and local councils - were held on 29 March.
In the House of Assembly, Zanu-PF won 97 seats, compared with 99 for the MDC plus another 10 for a smaller MDC faction.
It is the first time Mr Mugabe has lost control of the lower house of parliament in his 28-year rule since independence in 1980.
In the Senate, Zanu-PF and the combined opposition have 30 seats each.