(Updates number of deaths, arrests)
ADEN, Yemen, May 21 Three people were killed as a result of clashes on Thursday between Yemeni police and protesters marking the day when south Yemen's leader declared a breakaway state 15 years ago, residents and witnesses said.
They said one man was killed in the clashes and two others died in hospitals from wounds sustained during the clashes in a suburb of the southern city of Aden.
People in the south, home to most of Yemen's oil facilities, have long complained that northerners have abused a unity agreement to grab their resources and discriminate against them.
Ali Abdullah Saleh took power in former North Yemen in 1978 and has been president since union with the south in 1990. He fought a brief war in 1994 against southern separatists after their leader Ali Salem al-Beidh declared an end to the union.
Earlier this month, Saleh called on Yemenis to hold a dialogue to maintain national unity following a week of clashes in the south between the police and locals.
The poorest country in the Arabian Peninsula is trying to shake off an image of violence and lawlessness to promote tourism and foreign investment. It is battling al Qaeda, calls for secession in the south and Shi'ite rebels in the north.
"A man was shot dead next to me," one witness told Reuters, referring to the protest at a square in the Sheikh Othman suburb of Aden, the former capital of South Yemen.
Witnesses said several people were also wounded in clashes with the police who used teargas to disperse protesters.
Police and army forces banned gatherings in the area after dispersing the protest at the square where southern political figures were expected to address demonstrators, witnesses said.
Residents said the situation calmed down in the city after sporadic gunfire in the morning. Scores were arrested they said.
Demonstrations over army pensions turned violent in Aden in 2007 and job protests in the south degenerated into riots last year. Some southern leaders have openly called for secession. [ID:nL5593930]
Insecurity in Yemen has affected international companies developing the oil and gas sector, while attacks on foreigners -- including kidnappings by disgruntled tribesmen -- have hit tourism. (Reporting by Mohammed Mukhashaff; Writing by Inal Ersan; Editing by Charles Dick)