ATHENS, Greece (AP) _ Police broke up a news conference early Saturday while a Libyan diplomat was denying a Greek government statement that said he had asked the European Common Market to help defuse the U.S.-Libyan crisis.

''Libya didn't ask for any mediation, from Greece or anyone else,'' Libya's deputy foreign minister, Ahmad Shahati, told reporters. ''We can talk to anyone we want. Libya isn't so weak that it needs a mediator.''

A government statement issued Friday after Shahati met for one hour with Premier Andreas Papandreou said Shahati asked Greece and the 11 other members of the European Economic Community (Common Market) to mediate with the United States and Arab countries for a ''peaceful, lasting and just solution'' to conflicts in the Mediterranean.

''He (Shahati) stressed that Libya would be willing to receive and discuss all this with an EEC contact group,'' the statement said.

But Shahati, who had held an afternoon news conference when the government statement was released, made no mention of any request for mediation at that time.

He then boarded a Libyan executive jet to fly to Tripoli, the Libyan capital, but the plane had to return here when it developed engine trouble, officials at the Athens airport reported.

''Something blew in the oil pressure system soon after take off'' while the plane was flying over the town of Argos 60 miles south of Athens, one of the officials said.

A senior police officerm speaking with the condition he not be identified, denied reports circulating in Athens that the jet returned because of a bomb scare.

Several hours after he returned, Shahati called the news conference at the Athens Intercontinental Hotel.

He told reporters his plane returned for ''technical reasons'' and was disputing the government's version of his talks with Papandreou when Attica Police Chief Nikos Arkoudeas entered the room at 1 a.m. and ordered the journalists to leave.

Shahati was ushered out through a side door as Greek and foreign reporters scuffled with plainclothes policemen accompanying Arkoudeas, the district chief.

A senior police officer, Costas Kakavas, said the news conference was cut short on orders from the government.

Government spokesman Antonis Kourtis, who met with reporters later at the hotel, said, ''This place wasn't a secure area for Mr. Shahati to appear.'' The hotel was guarded by an estimated 200 policemen.

Kourtis also said the government stood by its statement on the Shahati- Papand reou talks.

The statement, issued by the Foreign Ministry, said Shahati ''asked that both Greece and the other EEC member states take action ... and contact interested parties and countries in the Arab world to find a peaceful, lasting and just solution of all the problems that arise from tension in the Mediterranean area.''

In the Netherlands, the Foreign Ministry announced the EEC was willing to mediate the U.S.-Libyan dispute. That announcement was made after the Greek government statement was released and before Shahati's late-night news conference.

A ministry spokeswoman in the Hague, who was not identified in line with government policy, noted no official Libyan request has been received. The Netherlands' foreign minister is the current Common Market president.

''We have to see if we can diminish the tensions between the United States and Libya,'' she said, but added: ''We agree with the United States that there should be an end to terrorism and especially state terrorism, and that Libya should put an end to that.''

She also noted that the EEC foreign ministers, in a communique issued Monday hours before U.S. warplanes bombed the Libyan cities of Tripoli and Benghazi, had opposed the use of force in the U.S.-Libyan conflict.

At a meeting Thursday in Paris, the Common Market foreign ministers pledged to boost diplomatic contacts to avoid further hostilities between Libya and the United States and urged the two nations to show ''the utmost restraint.''

The Greek government statement said that in his meeting with Shahati, Papandreou reiterated that stand, underlining ''the need for self-restraint toward finding a peaceful way out of the present temsion.''

Shahati, at the afternoon news conference, said he thanked Papandreou ''for the position Greece adopted in the European Economic Community - one that opposed the U.S. attack.''