NAIROBI, April 2 (Reuters) – Kenya’s biggest telecoms operator Safaricom lost a further percentage point of subscriber market share in the period to the end of December, its fifth straight quarterly fall, data from the sector regulator showed on Tuesday.

The firm, part-owned by South Africa’s Vodacom and Britain’s Vodafone, shed 0.9 percentage points of subscriber market share to 63.3 percent, compared with 71.9 percent in September 2017 when the losing streak started.

Safaricom, which is in a closed period ahead of full year results on May 2, did not comment on the latest figures.

The company began to lose market share after opposition leader Raila Odinga called for consumers to boycott Safaricom, accusing it of playing a role in an August 2017 presidential vote whose outcome he successfully challenged in court.

The losses have been sustained by an aggressive hunt for subscribers by the local unit of India’s Bharti Airtel , which is the second biggest operator in the country.

Airtel Kenya’s subscriber market share jumped to 23.4 percent at the end of December, from 14.9 percent in September 2017.

Airtel said in February it had agreed to merge with number three operator Telkom Kenya, adding to the pressure on Safaricom.

Investors have shrugged off the developments however, with Safaricom’s shares rising 22 percent this year to trade at 28.25 shillings ($0.2804).

According to regulator data in 2015, Safaricom had enjoyed the lion’s share of revenue, with more than 90 percent in key categories such as voice calls. The latest revenue data was not available.

Both Safaricom and Airtel have been increasing their quarterly user numbers but Airtel has reported faster growth in subscribers. ($1 = 100.7500 Kenyan shillings)

(Reporting by Duncan Miriri; Editing by Kirsten Donovan)