LUSAKA (Reuters) -Zambians voted for a new leader on Thursday with long queues pointing to a high turnout in an election showdown between President Edgar Lungu and main opposition rival Hakainde Hichilema that looks too tight to call.

       But as millions cast their ballots, social media platforms were restricted in the country, internet blockage observatory NetBlocks said.

       "Real-time network data confirm that social media and messaging platforms including Twitter, Facebook, Instagram and Messenger are now restricted in #Zambia on election day in addition to the earlier WhatsApp restriction," NetBlocks said in a tweet.

       Zambia Information and Communication Technology acting director-general Mulenga Chisanga did not answer calls for comment.

       The restriction of internet access could fuel tension and suspicion about the vote, which African and European observers said had been peaceful on Thursday.

       Lungu and Hichiema, who voted at different stations hours apart, were both confident of winning the vote and the close contest raised the possibility of a run-off.

       The electoral agency says it expects to declare a winner within 72 hours after polls close.

       Zambia, Africa's second-biggest copper producer, became the continent's first country during the coronavirus pandemic to default on its sovereign debt in November. Its economy is flagging.

       (Writing by MacDonald Dzirutwe; Editing by Joe Bavier, Raju Gopalakrishnan, Elaine Hardcastle and Angus MacSwan)