The human rights activist "was interrogated by the prosecution, who decided to extend his pre-trial detention by 15 days over the accusation of spreading rumours and false information," Mohammed al-Jishi said.
This accusation is linked to television interviews given by Rajab in 2014 and 2015, the lawyer said, adding a request to free him had been rejected.
On December 28, the prosecution said Rajab would remain in custody to be questioned over "spreading false news about the situation in the kingdom", despite being granted bail in another case over tweets deemed hostile to Bahrain and Saudi Arabia, for which the next hearing is on January 23.
Bahrain is part of a Saudi-led coalition since March 2015 battling Shiite Huthi rebels in Yemen.
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Rajab, who had been pardoned for health reasons last year, was rearrested in June and is on trial on a list of charges, including insulting a state institution and Saudi Arabia in online postings.
Rajab was questioned recently in custody over letters critical of the authorities that were published in September in The New York Times and in December in French daily Le Monde.
Rajab has been repeatedly detained for organising protests and publishing tweets deemed insulting to the Gulf state's Sunni authorities.
He previously served two years in jail on charges of taking part in unauthorised protests in the Shiite-majority kingdom.
Home to the US Navy's Fifth Fleet, Bahrain has been rocked by unrest since security forces crushed Shiite-led protests in 2011 demanding a constitutional monarchy and an elected prime minister.
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