Heavy gunfire erupted Tuesday morning around the home of Congo's top presidential challenger, a day after fighters trapped diplomats who had to be evacuated by U.N. peacekeepers.

U.N. spokesman Kemar Saiki said the United Nations has called on European forces to help secure the area. The European Union forces were already stationed in the region to maintain security during Congo's first multiparty presidential ballot in more than four decades.

CountryWatch: Congo (DRC)

Fighting first broke out in the capital of Kinshasa Sunday night as official results for the first round were announced. No candidate received a majority of votes, setting the stage for an October runoff between President Joseph Kabila and ex-rebel leader Jean-Pierre Bemba.

Troops loyal to the two fought Monday around Bemba's house in the northeastern Gombe district of Kinshasa. Bemba's political party said Kabila's guards attacked the house, drawing return fire from Bemba's guards. Bemba's helicopter caught fire inside the compound.

The party characterized the fighting as an attempt on Bemba's life.

A party spokesman said Bemba was evacuated from his house along with the foreign diplomats Monday, but troops continued to attack the candidate's house Tuesday.

"They're still attacking the residence of Vice President Bemba," said Dully Sesanga, Congo's planning minister and spokesman for Bemba's party.

The envoys evacuated from Bemba's residence included the head of the U.N.'s 17,500-troop peacekeeping mission, William Swing, and diplomats from the United States, France, China and other countries. U.N. spokesman Jean-Tobias Okala said 150 U.N. troops in 20 armored personnel took the diplomats from Bemba's home hours after they arrived for a meeting.

It was not clear if the diplomats were ambassadors or lower-ranking officials. The U.S. Embassy had no comment and others were not immediately reachable for comment.

In a bid to quell the violence, the army issued orders Monday for all soldiers in the Congolese capital to return to their barracks and lay down their arms.

At least two people died in fighting on Sunday.

With 16.9 million votes cast in the July 30 ballot, Kabila won 45 percent of the votes against 20 percent for Bemba, who is also a vice president in Kabila's transitional administration. The remainder of the votes cast were shared among 31 other candidates.