* Q1 production slips 4.9 pct on Nigeria, Libya * Nigeria still a critical issue - E&P head * Eni raises Mozambique gas estimate to 80 tcf MILAN, April 24 (Reuters) - Italian oil and gas giant Eni stuck to its growth forecast for the year after production fell almost 5 percent in the first quarter due to disruptions in Libya and Nigeria. "We confirm our growth... at $90 per barrel more than 3 percent, at $110 over 2 percent," Eni's head of exploration and production Claudio Descalzi said on a conference call. Eni is the biggest foreign oil producer in Africa and some analysts have expressed concern that unrest in parts of the continent could undermine prospects. Net profits in the first three months fell 39 percent to 1.43 billion euros ($1.86 billion) due in part to lower oil and gas production and a weak gas market. Since a siege at Algeria's In Amenas gas plant in January in which dozens of foreign hostages were killed, militants have struck foreign targets in fellow African oil producers Nigeria, Libya and Egypt. Eni, which produced 1.6 million barrels of oil equivalent per day in the first three months, lost around 20,000 boe/d in Nigeria in the period from sabotage and flooding. "We have to be clear, Nigeria is still a possible critical issue," Descalzi said. After a shut down for 10 days at the Mellitah oil and gas complex in Libya, Eni production in the country has been restored and stands at around 260,000 barrels per day. "We need to keep this average production," Descalzi said. Eni expects production growth this year to be boosted by ramp ups in Africa as well as a series of eight start ups, including the offshore Kashagan oil field in Kazakhstan. "Facilities will be ready to receive first oil in June and production will be in the following weeks," Descalzi said. Kashagan has turned into one of the world's most expensive oil development projects as delays pushed costs higher. FURTHER OUT State-controlled Eni, which has one of the strongest reserves replacement ratios among majors, has boosted its long-term prospects through a series of high-profile discoveries, including its massive gas find in Mozambique. Earlier on Wednesday Eni said it had completed the appraisal phase for its Mozambique acreage with more gas in place than first expected. It said it had discovered a total of 80 trillion cubic feet of gas in its Area 4 prospect. That compared to a previous estimate of 75 tcf. Mozambique's gas reserves have become hot property after Eni and U.S. Anadarko discovered around 150 tcf of natural gas, enough to supply Germany, Britain, France and Italy for 15 years. In March Eni agreed the sale of a 20 percent stake in its Mozambique offshore project to Chinese oil company CNPC in a deal worth $4.21 billion and which will leave the Italian major with 50 percent. Eni Chief Executive, Paolo Scaroni, recently said the group was open to talks with Gazprom after the Russian energy giant said it was interested in buying Eni gas assets in Mozambique.