(Reuters) - Japan's stricken Fukushima nuclear power plant has leaked more than 600 liters of water, forcing it to briefly suspend cooling operations at a spent-fuel pond over the weekend, but none is thought to have escaped into the ocean, the plant's operator and domestic media said Monday.

The Fukushima plant, on the coast north of Tokyo, was wrecked by a huge earthquake and tsunami in March last year, triggering the evacuation of around 80,000 people in the world's worst nuclear crisis in 25 years.

The operator of the complex, the Tokyo Electric Power Co (Tepco), reported two main leakages on its Web site on Sunday, one from a pump near the plant's office building and another from a back-up cooling system at reactor No.4.

The cooling water is from a filtrate tank for fire extinction and doesn't contain radioactive materials, Tepco said of the incident at reactor No. 4. It added that some water from the other leakage had flowed into a drain and we are examining whether this water has flowed into the ocean or not.

The Nikkei newspaper Monday quoted Tepco as saying around 40 liters had leaked from the pool-cooling system of the No. 4 reactor Sunday morning, with probably 600 liters of purified water leaking from another point. Water had also leaked at other facilities within the complex, the Nikkei added.

However, the Nikkei newspaper quoted Tepco Monday as saying that it believed no water had escaped into the sea.

The leakage is believed to have been caused by freezing due to cold weather, and the leaked water included radioactively contaminated water that has been purified, the Nikkei said in its online edition, quoting Tepco.

The contamination level is low.

(Reporting by Mark Bendeich; Editing by Kavita Chandran)

Earthquake Tsunami Japan Energy