UPDATE 1-Omantel CEO resigns as challenges mount

* Omantel CEO quits in surprise move, cites personal reasons

* Chief operating officer, Amer al-Rawas, named acting CEO (Adds details)

MUSCAT, March 29 (Reuters) - Oman Telecommunications Co OTL.OM (Omantel) Chief Executive Mohammed al-Wohaibi said on Sunday he had resigned from the country's largest telecoms for personal reasons.

The surprise resignation at Omantel comes after the government postponed plans to sell part of its controlling stake in the company in December and as Omantel faces increasing challenges over its investments in Pakistan.

"I have resigned for personal reasons," Wohaibi told Reuters, declining to elaborate. The company had earlier announced his resignation but did not provide any further details.

Shares in Omantel had eased 1.1 percent by 0845 GMT as the country's leading index .MSI slipped 1 percent.

Omantel's chief operating officer, Amer al-Rawas, is now acting chief executive, a company official told Reuters.

One analyst said he believed Wohaibi had been frustrated with the government's reluctance to sell a stake to private investors and the cautious approach of the company's expansion policies.

"He was unhappy when the government decided to pull out from selling the 25 percent share. He felt Omantel should be privatized at a much faster rate to compete better and increase efficiency," said Hilal al-Harthy, analyst at Jabreen Telecommunications Consultancy.

Omantel bought 488.8 million shares of Pakistan's Worldcall Telecom Ltd (WCTL.KA), equivalent to 65 percent of the company, in February 2008. The $193 million deal marks its biggest foreign investment so far.

But Worldcall's shares have fallen sharply since, with the company last valued at $29 million, according to Reuters data.

"The challenge for Omantel will be to make its Pakistan investment work ... Due to the legal, regulatory and the other issues in Pakistan, the company has not taken effective control of WTL," said Sunil Dhall, vice-president at Muscat-based Gulf Baader Capital Markets.

Omantel'S net profit fell 66.9 percent in the fourth quarter to about 9.744 million rials ($25.31 million) due to losses related to Worldcall.

The Omani government, which owns 70 percent of Omantel, said in 2008 that it could sell up to 30 percent of the firm. (Reporting by Saleh al-Shaibany; Writing by Asma Alsharif; Editing by Thomas Atkins)