The Nabucco gas pipeline project and energy co-operation in general was a key theme in separate talks between visiting Turkish foreign minister Ahmet Davutoglu and Bulgarian President Georgi Purvanov, Prime Minister Boiko Borissov and Foreign Minister Nikolai Mladenov.

Davutoglu was in Bulgaria on March 18 and 19 2010, in what the Bulgarian Foreign Ministry said was the first official visit by a Turkish foreign minister to Sofia in seven years.

Mladenov said that Bulgaria and Turkey shared common strategic interests, adding that there were no political problems between the two countries, only issues to be discussed.

The two countries had common interests in energy security in the Black Sea and Balkan region, Mladenov said. Building the Nabucco pipeline was top priority in bilateral relations, he said.

Davutoglu expressed thanks for Bulgaria's support for Turkey's future membership of the European Union, and recalled that Turkey had strongly supported Bulgaria joining Nato.

In the talks between Davutoglu and Mladenov, the possibility was discussed of finding a common approach in areas such as the Caucasus, Middle East and Mediterranean.

On the economic front, the two foreign ministers discussed the possibilities to increase Turkish investment in Bulgaria, which currently amounts to about $1 billion.

Purvanov, in a statement after meeting Davutoglu, said that it was important that the two sides wanted to address existing problems in a spirit of mutual understanding.

Apart from also discussing Nabucco, Purvanov raised the issue of Bulgarian Exarchate properties in Turkey, and compensation for refugees, the latter an issue - dating back to the time around the collapse of the Ottoman Empire - that long has been a sore point between Sofia and Ankara, with Bulgaria demanding the payment of compensation for families displaced because of Ottoman actions.

Recently, there was a spat between the two countries when minister for Bulgarians abroad Bozhidar Dimitrov raised the issue publicly, saying that compensation should be paid or Bulgaria would withdraw its support for Turkish EU accession - an act for which he was slapped down by Prime Minister Boiko Borissov.

Turkish president Abdullah Gul is expected to visit Bulgaria in October this year, President Purvanov's office said.

Bulgaria and Turkey are campaigning to have two houses of worship, the mosque in Plovdiv and the St Stephan church in Istanbul, included in the Unesco list of world heritage sites.