Toyota Motor on Wednesday said fourth quarter net profit tumbled 77 percent after Japan's massive earthquake and tsunami heavily disrupted production and as the yen strengthened.

Like many of its Japanese peers, Toyota declined to give a forecast for the current year as it assesses the impact of the March 11 disaster, but it said it expected output to "normalise" globally in June, earlier than first thought.

The 9.0-magnitude earthquake and the resulting tsunami hammered production, shattered supply chains and crippled electricity-generating facilities, including a nuclear power plant at the centre of an ongoing atomic emergency.

Amid power and parts shortages, Toyota had announced production disruptions domestically and in the United States, European Union, China and Australia because of the crisis, temporarily slowing output or shutting plants.

Toyota president Akio Toyoda told reporters: "Our efforts to bring production to normal are advancing. At home and overseas, we are expected to recover some 70 percent of normal levels by June."

His prediction is more optimistic than last month's forecast of normalisation by July in Japan, and worldwide by August.

However, many analysts say the output drop may see Toyota fall behind General Motors in sales this year as the Japanese giant works to put a recall crisis involving millions of vehicles behind it.

Many component manufacturers in Japan are based in the worst-hit northeast region, where facilities were damaged by the earthquake or inundated by the giant wave that followed. Toyota said it is still short of 30 key parts.

It said net profit for January-March dived 77 percent to 25.4 billion yen ($314 million) while operating profit tumbled 52 percent to 46.1 billion yen.

For the year that ended in March, operating profit more than tripled from a year earlier to 468.2 billion, but was cut by 110 billion yen ($1.36 billion) as a result of the March 11 disasters.

Toyota said net profit in the year to March doubled to 408.1 billion yen, missing a February forecast of 490 billion yen.

The automaker did not give an estimate for the current year, saying that it needed more time to assess the true scale of impact of the quake on production and sales.

A strong yen, which hit a post-war high of 76.25 against the dollar in the aftermath of the earthquake, has also hit repatriated earnings.

Toyota faced the prospect of a Moody's downgrade to its long-term credit rating last month because of the seismic disaster.

Standard & Poor's cut its rating on the automaker earlier this year.

Analysts say Toyota is particularly exposed in terms of its thin operating margins in comparison with its peers, partly due to quality-related expenditures as it looks to recover from the impact of millions of safety recalls.

Previously lauded for its safety, Toyota became mired in crisis when it recalled nearly nine million autos between late 2009 and February last year due to brake and accelerator defects alleged to have caused dozens of deaths.

The crisis dealt a huge blow to the firm's reputation, prompting predictions it would lose market share as it tightened its recall policy to encompass around 16 million vehicles between late 2009 and January this year.

In January Toyota announced global sales of 8.42 million vehicles in 2010, just ahead of General Motors' 8.39 million, but analysts say the impact of the March 11 disasters will pressure its position as the world's biggest carmaker.

Toyota shares on Wednesday closed up 0.61 percent at 3,270 yen but are 10.5 percent below levels before the disaster, compared with around 8 percent at Honda and 4 percent at Nissan as of Wednesday's close.

In April Honda said its net profit for the fourth quarter ended March fell 38.3 percent from a year earlier, due to costs related to the quake as well as the impact of a strong yen.