Novak Djokovic was far from his fluent best but the defending champion did enough to beat Germany's Philipp Kohlschreiber in straights sets and move safely into the second round at Wimbledon.

Djokovic was playing his first competitive match since his shock French Open final defeat to Stan Wawrinka just over three weeks ago and there were certainly signs of rust from the world number one.

Kohlschreiber, however, was too generous at the crucial moments on Centre Court and Djokovic was able to seal a 6-4 6-4 6-4 victory.

There will certainly be tougher tests to come if he is to claim a third Wimbledon title, but Djokovic will be relieved to overcome a potentially tricky opponent in Kohlschreiber, who took Roger Federer to a final set tie-break before losing in Halle earlier this month.

The world number 33 caused Djokovic problems with his devilish slice backhand and he had three break points in the seventh game of the first set but was unable to capitalise, with the first drifting away after a close review.

Djokovic was more clinical, as two Kohlschreiber double faults allowed him to break in the 10th game and sneak the first set.

There were plenty of loose shots from the Australian Open champion, with a number of backhands flying long and simple forehands finding the net, but again Djokovic raised his level just when he needed to.

Leading 5-4, he produced an exquisite lob and a superb backhand pass before breaking Kohlschreiber again to take a two-set advantage.

The third set followed a similar pattern as Kohlschreiber's serve continued to let him down under pressure and Djokovic broke to secure a comfortable win in just over two hours.

Djokovic was grateful for the support of a "bird from Belgrade" after a mischievous sparrow flew on to the court and strutted around the tram-line for most of the match.

"From where I come from, from the capital of Serbia, Belgrade, there's a special sparrow bird - I believe this bird came all the way from Belgrade to help me," Djokovic said.

"But I was feeling for its safety honestly a few times. I couldn't not notice it. I mean it just loves tennis, I guess.

"At one point Kohlschreiber was serving at the advantage side, between the first and second serve, and the bird landed literally very close to the sideline.

"She stayed there until I won that point. So I said, 'Be my guest, stay around, if you want.'

"It was funny to see that. We had birds, mostly birds and different animals come in and out from the court, but the sparrow bird from Belgrade really stayed for the entire match."

"Do you want to say I'm cheating, my team? I'm really trying to figure out what's behind this"

"Did I feel any rust? Not much," Djokovic said.

"Honestly, I thought I started the match really well, breaking Philipp, losing the serve right away.

"All three sets were decided in the 10th game. After I broke him to win the first set and the second set, it was the same situation.

"I felt like in the third, as well, that's where maybe I can have a mental edge over him. He missed a couple of shots.

"I thought my return was exceptionally good from my side, serving efficiently - just overall a great performance against a quality opponent."

Djokovic, who now faces Finland's Jarkko Nieminen in the second round, has come under fire after his coach Boris Becker suggested they had secret signals to communicate with each other during matches.

ATP rules state players are not allowed to receive "communications of any kind, audible or visible" during a tournament match and Djokovic was visibly annoyed when the issue was brought up again.

"I don't understand what you really want," Djokovic said.

"Do you want to say I'm cheating, my team? I'm really trying to figure out what's behind this. I mean, are you asking only me or are you asking other players, as well?

"I don't understand what I can say, what I haven't said already before. I'm going to repeat myself.

"I'm going to say that there are certain ways of communication which is encouragement, which is support, which is understanding the moment when to clap or say something that can lift my energy up, that can kind of motivate me to play a certain point. But it's all within the rules."

Djokovic added: "Of course, I accept the fact if my coach, Boris or Marian, do something that is against the rules, I have no complaint about the code violation that I get for coaching."

Nick Kyrgios has insisted he was calling himself "dirty scum" and not the umpire in his routine victory over Diego Schwartzman.

Colourful Australian Kyrgios dispatched Argentina's Schwartzman 6-0 6-2 7-6 (8/6) to progress to Wimbledon's second round, but risked a fine for his on-court outburst.

Kyrgios denied directing his outburst at umpire Mohamed Lahyani, after threatening to stop play when contesting a call in the third set.

"Wouldn't bother me one bit," said Kyrgios when asked if he feared receiving a fine for his behaviour. I wasn't referring to the ref at all there, it was towards myself.

"But, yeah, obviously I knew you guys were going to ask me about that."

When quizzed on why he called himself "dirty scum", Kyrgios replied: "Why are you so caught up about the question? Because I can."

Kyrgios burst on to the tennis world's major consciousness by dumping Rafael Nadal out of the fourth round at Wimbledon last year, and has improved rapidly since.

The world number 29 will now meet the winner of Argentina's Juan Monaco and Germany's Florian Mayer in the second round at SW19.

Kyrgios attempted to explain away the on-court delay by claiming questionable calls "shouldn't be something that can be taken lightly".

"I just wanted to get the guy that was in charge of the referees," he said.

"He was already sitting out there. I'm not too fussed about the call to be honest, but if it was more a crucial time in the match, or deeper in the tournament, that could swing things.

"It shouldn't be something that can be taken lightly. You've got to make the right call there.

"He knew it was a replay, the guy sitting off the court. He ultimately said, 'it's the ref's call. I really couldn't do anything about it."

Liam Broady produced a remarkable fightback to boost British hopes at Wimbledon with a thrilling five-set victory over Marinko Matosevic.

Stockport's Broady was the first Briton in action in this year's tournament, and turned a two-set deficit on its head to set up a second-round clash with Belgium's David Goffin.

Broady belied a poor start and a 44-place deficit in the world rankings to see off Australia's "Mad Dog" Matosevic 5-7 4-6 6-3 6-2 6-3 for his first Wimbledon victory.

Lleyton Hewitt battled to the bitter end but was unable to prevent his Wimbledon singles career finishing with a dramatic five-set defeat to Nieminen.

Hewitt, who is retiring after the Australian Open next year, will be forever remembered for his irrepressible fighting spirit and the 2002 champion typically saved three match points to extend an incredible final set on Court 2.

Nieminen, however, also making his last appearance at SW19, held his nerve to seal a 3-6 6-3 4-6 6-0 11-9 victory and book a second-round match-up with defending champion Djokovic.

Hewitt twice led the Fin after winning the first and third sets but the Australian called two medical time-outs in the decider and finally, after exactly four hours on court, his resistance crumbled.

It means Hewitt has won 41 matches and lost 16 in his 17 appearances at the All England Club, and he arguably saved his most dramatic contest until last.

Meanwhile, Swiss fourth seed Stan Wawrinka beat Portugal's Joao Sousa 6-2 7-5 7-6 (7/3).

Fifth seed Kei Nishikori needed five sets to beat Italy's Simone Bolelli and there were also wins for Croatia's Marin Cilic, Bulgaria's Grigor Dimitrov and Canadian Milos Raonic.