April 7 (Reuters) - Zimbabwe's political situation has evolved rapidly since March 29 elections in which President Robert Mugabe lost control of parliament for the first time in his 28-year rule.

Below are answers to some key questions as tension rises between Mugabe's ruling ZANU-PF party and the opposition Movement for Democratic Change (MDC).

WHAT RESULTS ARE KNOWN?

Official results give the MDC 99 seats in parliament, a breakaway opposition faction 10 and ZANU-PF 97. One seat went to an independent.

No presidential results have so far been released.

Senate results show contested seats split 30-30 between the combined opposition and the ruling party. Control of the 93-seat Senate will depend on who becomes president, with powers to directly appoint 15 members and strongly influence who gets other positions.

The MDC said its leader Morgan Tsvangirai won the presidential poll outright. ZANU-PF projections show that although he won, he fell short of the absolute majority needed for first-round victory.

WHY ARE DELAYS SIGNIFICANT?

In past polls, results emerged quickly. This time there is no presidential outcome after nine days. According to electoral rules, a runoff between Tsvangirai and Mugabe should be held within three weeks of the results announcement. The longer the delay, the more time Mugabe has to organise his fightback.

WHAT IS MUGABE'S STRATEGY?

A few days ago, Mugabe looked badly wounded by the parliamentary defeat and there was speculation he would step down. But strong backing by security chiefs appears to have strengthened the government's resolve to counter-attack.

ZANU-PF's emerging strategy appears to be to:

- Challenge some parliamentary results through the courts and demand a recount in the presidential vote because of alleged irregularities.

- Delay the presidential result and any runoff. ZANU-PF has asked electoral officials to defer presidential results pending a recount. There are suggestions Mugabe will use presidential powers to extend the interval before a runoff to 90 days.

- Deploy pro-government militias including youth brigades and the feared independence war veterans to intimidate MDC supporters before a new vote. The veterans, awarded big pensions and formerly white-owned farms under Mugabe's controversial land reform programme, have already emerged to strongly back him.

WHAT IS MDC STRATEGY?

- The MDC has gone to the High Court to try to force the electoral commission to release the results. The court must first rule on whether it has the authority to rule on the MDC application. It was expected to decide on Monday.

- The MDC has repeatedly said Tsvangirai won outright and should be declared president. It says Mugabe would be humiliated in a runoff and a recount at this stage would be illegal.

- It is making frequent statements to keep the Zimbabwe situation high on the world agenda and has appealed for foreign help to end Mugabe's rule.

- Tsvangirai has appealed to former colonial power Britain, the United States and regional heavyweight South Africa to intervene to help remove Mugabe.

- The MDC will try to persuade millions of Zimbabwean economic refugees to return from abroad to vote in a runoff.

WHAT WOULD HAPPEN IN A RUNOFF?

The opposition says it would unite behind Tsvangirai, which should, on paper, produce an overwhelming victory based on first round results. But Mugabe's control of state power, security forces and militia could make this much less certain.

WHAT IF MUGABE WINS?

If Mugabe wins a runoff or first round results are revised to give victory to ZANU-PF, this is certain to be rejected by the MDC and some of its supporters could take to the streets. However a Kenyan scenario of prolonged protests and bloodshed seems unlikely because of the power of the security forces.

An outcry in the West and increased sanctions against Mugabe and his entourage would be likely. But such measures have so far had little effect on changing things in Zimbabwe.

Some analysts believe Mugabe would be forced to carry out some reforms, even if he stayed in power, to try to ease the dire economic crisis and diplomatic isolation, but he showed no sign of readiness to do so during his campaign.

WHAT IF TSVANGIRAI WINS?

If Tsvangirai wins and he can resist any violent crackdown by ZANU-PF militants and security forces, foreign powers are expected to flood Zimbabwe with aid to rescue the economy.

Former colonial ruler Britain says it is working with the United States, IMF, World Bank and European Union to prepare a $1 billion recovery plan. Investors are expected to flood back into the once-prosperous nation at the prospect of big returns.

One option would be for Tsvangirai to form a national unity government with ZANU-PF moderates. (Reporting by Barry Moody; editing by Matthew Tostevin)

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