Police in the Gaza Strip, which Hamas controls, shut the offices of Palestinian telecoms provider Jawwal in Gaza City and left notices proclaiming it was "on the orders of the (Hamas) public prosecutor", an AFP correspondent said.
The company confirmed the closure, which was ordered last week by the public prosecutor, Ismail Jabr, for alleged "tax evasion".
Jawwal's parent company Palestinian Telecommunication Group (PalTel) closed all its branches in the besieged coastal enclave "to protest against the shutting of the Gaza headquarters", an official told AFP on condition of anonymity.
Jawwal last week insisted it was not "avoiding any (payment) commitments".
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Omar Shaaban, an economist who heads the Gaza-based think-tank Palthink, said the closure could mean a halt to all mobile phone services in the Strip.
"There is no alternative in Gaza to the services provided by this company," he said of Jawwal, one of the principle telecoms providers in the Palestinian territories.
The PA slammed the closure as "aggravating division" and "a flagrant violation of Palestinian law".
A years-long split between Hamas and the PA, which is dominated by rival political party Fatah, has caused previous financial crises in the war-wracked territory.
Last year, Hamas closed banks for several days after a dispute with the PA over wages.
Under an April 2014 unity agreement, Hamas and Fatah pledged to put their differences behind them, transferring adminstration of Gaza to the PA, including collection of taxes and the running of ministries.
A war in Gaza between Hamas and Israel last year dealt further setbacks to prospects of Palestinian reconciliation.