African mobile phone use has rocketed in recent years
The Kenyan government has launched a share flotation of Safaricom, the country's largest mobile phone network.
President Mwai Kibaki's administration is selling off a 15% stake in the company, a move which is expected to raise about $750m (£376m).
Analysts said the share sale had been greatly oversubscribed, with ordinary citizens the bulk of the buyers.
Opposition parties had tried to delay the issue because of uncertainty over Safaricom's other shareholders.
It will be the largest flotation ever on the Kenyan stock market.
The BBC's Karen Allen in Nairobi says that banks were packed with investors looking to buy shares.
She says that by the time the sale is finished, one in 10 working Kenyans is expected to own shares.
While the government insists it currently owns 60% of Safaricom with the other 40% in the hands of UK giant Vodafone, opposition groups say another firm called Mobitelea also has an interest.
Registered in Guernsey in the Channel Islands, Mobitelea's owners remain unknown.
Media reports in Kenya have speculated that Mobitelea owns as much as 10% of Safaricom.
"They [the government] should have told this country who Mobitelea is, and whether they acquired the shares procedurally," opposition MP William Ruto told the BBC.
Kenyan Finance Minister reiterated that Mobitelea was not a direct Safaricom shareholder.
Safaricom is the most profitable company in the whole of east Africa, enjoying profits of $370m last year.
Employing more than 1,000 people, its 2007 revenues totalled $700m.
The sale comes even though Kenya does not have a full cabinet, as negotiations continue following last year's disputed elections.
Read a selection of your comments on this story:
The government should have revealed the owners of Mobitelea before proceeding with selling the shares. What we see today means that the government is not answerable to its people, Something which is quite unfortunate.
Mark, Nairobi, Kenya
Most of the people in the opposition do not invest in stock market. They fear central part of Kenya will benefit more.
Simon Kuria, Thika, Kenya
Sure, I was looking forward to this sale, but the uncertainties concerning Mobitelea has made me think otherwise. It is never too late to do what is right. Why the secrecy about this company? I am sure the offer could have been more successful if we were more honesty and transparent in this whole thing.
Vincent Kimosop, Nairobi, Kenya