TUNIS, Sept 30 (Reuters) - Presidents Isayas Afewerki of Eritrea and Ibrahim Bare Mainassara of Niger arrived by air in Libya on Wednesday despite a U.N. embargo on flights to and from the North African country imposed in connection with the bombing of a Pan Am airliner over Lockerbie, Scotland, in 1988.

Libyan state television, monitored in Tunis, broadcast the arrival of Mainassara's aircraft at the Libyan coastal city of Sirte, some 450 km (280 miles) east of Tripoli.

It later broadcast live the arrival at Sirte airport of the Eritrean president aboard a Libyan Arab Airlines aircraft.

Both were greeted at the airport by one of Gaddafi's lieutnants, Abu Bakr Jaber Yunes.

Afewerki and Mainassara arrived less than 24 hours after Ugandan President Yoweri Museveni for talks with Libyan leader Muammar Gaddafi.

Sudan, which has close ties with Libya, on Monday called a general mobilisation to confront what it said were attacks by Uganda and Eritrea in southern Sudan.

It is not clear whether a summit was planned. On Tuesday, Gaddafi received an unnamed Sudanese minister who also flew to Libya despite an air ban, the television earlier reported.

``My visit is part of our tradition of consultations...within the framework of the Saharan countries' grouping,'' Mainassara said on arrival.

The grouping was established last year with the aim of boosting ties between its members, which also include Chad, Burkina Faso, Mali and Sudan. It is chaired by Gaddafi.

Mainassara and Afewerki made a similar flights to Libya a month ago to attend the celebrations of the 29th anniversary of the Libyan revolution.

At least eight African head of state flew to Libya this month after an Organisation of African Unity resolution last June called on member states to ignore the air embargo imposed on Libya in 1992.

The ban was part of U.N. sanctions imposed on Libya for failing to hand over two Libyan suspects in the bombing of the Pan Am Boeing 747 in which 270 people were killed.