Authorities in control of Libya's capital on Friday declared a "maximum state of emergency" after a U.N.-backed unity government that they reject said its members would head to Tripoli to begin work.

The city is under the control of an administration backed by armed groups including Islamists that is not internationally recognized.

At least seven people were killed in clashes Wednesday west of Tripoli between tribesmen and forces loyal to Libya's unrecognized government, an army officer said.

U.N envoy Martin Kobler said he was prevented from traveling Wednesday to the Libyan capital for his work on the installation of a new unity government.

Tripoli is under the control of an unrecognized administration backed by a coalition of militias including Islamists that opposes the new government from starting work inside the country.

Libya's neighbors on Tuesday called on the U.N.-backed government to take office as quickly as possible in Tripoli to help tackle the growing influence of jihadists threatening their stability.

The call was made at a ministerial meeting hosted by Tunisia and attended by delegates from Algeria, Chad, Egypt, Niger and Sudan, as well as the U.N. envoy to Libya.

Tunisia reopened its border crossings with Libya on Tuesday after a two-week closure in response to a deadly jihadist attack on a town near the frontier, the interior ministry said.

The move came as Tunisia hosted talks with other countries neighboring Libya on the threat posed by the growing Islamic State (IS) group presence in the lawless North African nation.

Leaders from six EU nations led by Britain were holding talks Friday on how to tackle migration from Libya at a Brussels summit focused on dealing with an unprecedented influx of people fleeing war in Syria.

British Prime Minister David Cameron was hosting a meeting with leaders from France, Germany, Italy, Spain, Malta and Federica Mogherini, the European Union's foreign policy chief, his spokeswoman said.

Libyan coastguards and navy special forces on Thursday rescued 187 African migrants and found four bodies after a fire on a boat headed for Europe, a navy spokesman said.

Colonel Ayoub Qassem, quoted by a news agency operated by Libya's unrecognized authorities in Tripoli, said the rescue took place six nautical miles off Sabratha, 70 kilometers (45 miles) west of the capital.

Libya's unrecognized authorities in control of Tripoli warned a new U.N.-backed unity government on Wednesday that it would not be welcome in the capital.

"A government that has been imposed from abroad without the consensus of Libyans... has no place amongst us," the so-called Tripoli government said in a statement.

Nearly 2,000 migrants and two corpses have been recovered from people smugglers' boats off Libya since Tuesday, Italy's coastguard said Wednesday.

Further rescue operations were ongoing, a spokesman told AFP.

Two Italians kidnapped last July in Libya returned to Italy on Sunday to a mute homecoming, amid questions over why two others snatched with them were killed.

Gino Pollicardo, 55, and Filippo Calcagno, 65, were met by relieved relatives at Rome's Ciampino airport in the early hours and were whisked away to be debriefed by Italy's foreign ministry and intelligence services.