Security has been tightened at and around Tanzania's police headquarters in Dar es Salaam Tuesday to fend off likely supporters of opposition leader Edward Lowassa.

The former Prime Minister had been summoned to appear before the Director of Criminal Investigation (DCI) Tuesday at 10am over unspecified reasons.

Mr Lowassa arrived at the police headquarters in a convoy of four vehicles with two police cars following.

A heavy police presence was seen along the road leading to the headquarters, with others patrolling the area on Tuesday morning. Journalists were barred from taking photographs.

On Monday, while confirming the summons, Mr Lowassa said he was served with the directive through a letter.

“I have received the letter which directs me to report to the DCI offices tomorrow but I still don’t know the reasons behind it,” he said on Monday.

The former premier, however, said he suspected he would be interrogated over remarks he had made on Friday during Iftar -- the evening meal that breaks the daily fast during Ramadhan -- address in Dar es Salaam.

Mr Lowassa had called on President John Magufuli to intervene in speeding up a court case in which Muslim clerics, arrested in Zanzibar over alleged terrorism links, have been in custody for over four years awaiting trial.

“I am not sure if this could be the reason but I am just guessing. But the truth will be clear by tomorrow when I will see the DCI,” he said.

Mr Lowassa contested in the 2015 General Election where he lost to President Magufuli.

During his campaign he had pledged to order the release of the clerics should he have won. 

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